#include <bits/stdc++.h>

 using namespace std;

 #define INIT() ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);

 #define Rep(i,n) for (int i = 0; i < (int)(n); ++i)

 #define For(i,s,t) for (int i = (int)(s); i <= (int)(t); ++i)

 #define rFor(i,t,s) for (int i = (int)(t); i >= (int)(s); --i)

 #define ForLL(i, s, t) for (LL i = LL(s); i <= LL(t); ++i)

 #define rForLL(i, t, s) for (LL i = LL(t); i >= LL(s); --i)

 #define foreach(i,c) for (__typeof(c.begin()) i = c.begin(); i != c.end(); ++i)

 #define rforeach(i,c) for (__typeof(c.rbegin()) i = c.rbegin(); i != c.rend(); ++i)

 #define pr(x) cout << #x << " = " << x << "  "

 #define prln(x) cout << #x << " = " << x << endl

 #define LOWBIT(x) ((x)&(-x))

 #define ALL(x) x.begin(),x.end()

 #define INS(x) inserter(x,x.begin())

 #define UNIQUE(x) x.erase(unique(x.begin(), x.end()), x.end())

 #define REMOVE(x, c) x.erase(remove(x.begin(), x.end(), c), x.end()); // 删去 x 中所有 c

 #define TOLOWER(x) transform(x.begin(), x.end(), x.begin(),::tolower);

 #define TOUPPER(x) transform(x.begin(), x.end(), x.begin(),::toupper);

 #define ms0(a) memset(a,0,sizeof(a))

 #define msI(a) memset(a,0x3f,sizeof(a))

 #define msM(a) memset(a,-1,sizeof(a))

 #define MP make_pair

 #define PB push_back

 #define ft first

 #define sd second

 template<typename T1, typename T2>

 istream &operator>>(istream &in, pair<T1, T2> &p) {

     in >> p.first >> p.second;

     return in;

 }

 template<typename T>

 istream &operator>>(istream &in, vector<T> &v) {

     for (auto &x: v)

         in >> x;

     return in;

 }

 template<typename T>

 ostream &operator<<(ostream &out, vector<T> &v) {

     Rep(i, v.size()) out << v[i] << " \n"[i == v.size()];

     return out;

 }

 template<typename T1, typename T2>

 ostream &operator<<(ostream &out, const std::pair<T1, T2> &p) {

     out << "[" << p.first << ", " << p.second << "]" << "\n";

     return out;

 }

 inline int gc(){

     static const int BUF = 1e7;

     static char buf[BUF], *bg = buf + BUF, *ed = bg;

     if(bg == ed) fread(bg = buf, , BUF, stdin);

     return *bg++;

 } 

 inline int ri(){

     int x = , f = , c = gc();

     for(; c<||c>; f = c=='-'?-:f, c=gc());

     for(; c>&&c<; x = x* + c - , c=gc());

     return x*f;

 }

 template<class T>

 inline string toString(T x) {

     ostringstream sout;

     sout << x;

     return sout.str();

 }

 inline int toInt(string s) {

     int v;

     istringstream sin(s);

     sin >> v;

     return v;

 }

 //min <= aim <= max

 template<typename T>

 inline bool BETWEEN(const T aim, const T min, const T max) {

     return min <= aim && aim <= max;

 }

 typedef long long LL;

 typedef unsigned long long uLL;

 typedef vector< int > VI;

 typedef vector< bool > VB;

 typedef vector< char > VC;

 typedef vector< double > VD;

 typedef vector< string > VS;

 typedef vector< LL > VL;

 typedef vector< VI > VVI;

 typedef vector< VB > VVB;

 typedef vector< VS > VVS;

 typedef vector< VL > VVL;

 typedef vector< VVI > VVVI;

 typedef vector< VVL > VVVL;

 typedef pair< int, int > PII;

 typedef pair< LL, LL > PLL;

 typedef pair< int, string > PIS;

 typedef pair< string, int > PSI;

 typedef pair< string, string > PSS;

 typedef pair< double, double > PDD;

 typedef vector< PII > VPII;

 typedef vector< PLL > VPLL;

 typedef vector< VPII > VVPII;

 typedef vector< VPLL > VVPLL;

 typedef vector< VS > VVS;

 typedef map< int, int > MII;

 typedef unordered_map< int, int > uMII;

 typedef map< LL, LL > MLL;

 typedef map< string, int > MSI;

 typedef map< int, string > MIS;

 typedef set< int > SI;

 typedef stack< int > SKI;

 typedef queue< int > QI;

 typedef priority_queue< int > PQIMax;

 typedef priority_queue< int, VI, greater< int > > PQIMin;

 const double EPS = 1e-;

 const LL inf = 0x7fffffff;

 const LL infLL = 0x7fffffffffffffffLL;

 const LL mod = 1e9 + ;

 const int maxN = 1e4 + ;

 const LL ONE = ;

 const LL evenBits = 0xaaaaaaaaaaaaaaaa;

 const LL oddBits = 0x5555555555555555;

 struct Edge{

     int from, to, w;

     int et, lt;

 };

 istream& operator>> (istream& in, Edge &x) {

     in >> x.from >> x.to >> x.w;

     return in;

 }

 struct Vertex{

     int in, out, value, nxt;

     VI next, prev;

     int et, lt;

     void clear() {

         value = in = out = ;

         nxt = inf;

         next.clear();

         prev.clear();

         et = ;

         lt = inf;

     }

 };

 int N, M, S, T;

 Vertex V[maxN];

 vector< Edge > E;

 VI topo, ans;

 void addEdge(Edge &x) {

     V[x.from].next.PB(E.size());

     V[x.to].prev.PB(E.size());

     ++V[x.to].in;

     ++V[x.from].out;

     E.PB(x);

 }

 void init() {

     For(i, , N) V[i].clear();

     E.clear();

     topo.clear();

     ans.clear();

 }

 void TopoSort() {

     SKI sk;

     For(i, , N) if(!V[i].in) sk.push(i);

     while(!sk.empty()) {

         int tmp = sk.top(); sk.pop();

         topo.PB(tmp);

         Rep(i, V[tmp].next.size()) {

             Edge &e = E[V[tmp].next[i]];

             if(!--V[e.to].in) sk.push(e.to);

         }

     }

 }

 // 在拓扑排序的基础上松弛

 inline void relax() {

     rFor(i, topo.size() - , ) {

         Rep(j, V[topo[i]].prev.size()) {

             Edge &e = E[V[topo[i]].prev[j]];

             if(V[e.from].value < V[e.to].value + e.w || V[e.from].value == V[e.to].value + e.w && e.to < V[e.from].nxt) {

                 V[e.from].value = V[e.to].value + e.w;

                 V[e.from].nxt = e.to;

             }

         }

     }

 }

 int main(){

     //freopen("MyOutput.txt","w",stdout);

     //freopen("input.txt","r",stdin);

     INIT();

     while(cin >> N >> M) {

         init();

         For(i, , M) {

             Edge t;

             cin >> t;

             addEdge(t);

         }

         TopoSort();

         S = topo.front();

         T = topo.back();

         relax();

         int t = S;

         while(t != inf) {

             ans.PB(t);

             t = V[t].nxt;

         }

         cout << V[S].value << endl;

         Rep(i, ans.size() - ) cout << ans[i] << " " << ans[i + ] << endl;

     }

     return ;

 }