Problem Description

Dandelion's uncle is a boss of a factory. As the spring festival is coming , he wants to distribute rewards to his workers. Now he has a trouble about how to distribute the rewards.
The workers will compare their rewards ,and some one may have demands of the distributing of rewards ,just like a's reward should more than b's.Dandelion's unclue wants to fulfill all the demands, of course ,he wants to use the least money.Every work's reward
will be at least 888 , because it's a lucky number.

 

Input

One line with two integers n and m ,stands for the number of works and the number of demands .(n<=10000,m<=20000)
then m lines ,each line contains two integers a and b ,stands for a's reward should be more than b's.

 

Output

For every case ,print the least money dandelion 's uncle needs to distribute .If it's impossible to fulfill all the works' demands ,print -1.

 

Sample Input

 

Sample Output

 

Author

dandelion

 

#include<iostream>

#include<algorithm>

#include<cstdlib>

#include<sstream>

#include<cstring>

#include<cstdio>

#include<string>

#include<deque>

#include<stack>

#include<cmath>

#include<queue>

#include<set>

#include<map>

using namespace std;

#define INF 0x3f3f3f3f

#define MM(x) memset(x,0,sizeof(x))

#define MMINF(x) memset(x,INF,sizeof(x))

typedef long long LL;

const double PI=acos(-1.0);

const int M=20010,N=10010;

struct info

{

    int to;

    int pre;

}E[M];

int head[N],cnt;

int deg[N];

int level[N],vis[N];

void init()

{

    memset(head,-1,sizeof(head));

    cnt=0;

    MM(deg);

    MM(level);

}

void add(int s,int t)

{

    E[cnt].to=t;

    E[cnt].pre=head[s];

    head[s]=cnt++;

}

void dfs(int s,int tl)

{

    vis[s]=1;

    for (int i=head[s]; i!=-1; i=E[i].pre)

    {

        int v=E[i].to;

        if(!vis[v])

        {

            cnt++;

            level[v]=max(level[v],tl+1);

            dfs(v,tl+1);

        }

    }

    vis[s]=0;

}

queue<int>Q;

int main(void)

{

    int n,m,i,j,a,b,c;

    while (~scanf("%d%d",&n,&m))

    {

        init();

        for (i=0; i<m; i++)

        {

            scanf("%d%d",&a,&b);

            add(b,a);

            deg[a]++;

        }

        while (!Q.empty())

        	Q.pop();

        int C=0;

        for (i=1; i<=n; i++)

        {

            if(!deg[i])

            {

                Q.push(i);

                C++;

            }

        }

        while (!Q.empty())

        {

            int now=Q.front();

            Q.pop();

            dfs(now,0);

        }

        for (i=1; i<=n; i++)

        {

            if(!level[i])

                C--;

        }

        if(C)

            puts("-1");

        else

        {

            int r=0;

            for (i=1; i<=n; i++)

                r+=888+level[i];

            printf("%d\n",r);

        }

    }

    return 0;

}

#include<iostream>

#include<algorithm>

#include<cstdlib>

#include<sstream>

#include<cstring>

#include<cstdio>

#include<string>

#include<deque>

#include<stack>

#include<cmath>

#include<queue>

#include<set>

#include<map>

using namespace std;

#define INF 0x3f3f3f3f

#define MM(x) memset(x,0,sizeof(x))

#define MMINF(x) memset(x,INF,sizeof(x))

typedef long long LL;

const double PI=acos(-1.0);

const int M=20010,N=10010;

struct info

{

    int to;

    int pre;

    int dx;

}E[M];

int head[N],cnt,deg[N];

int d[N];

void init()

{

    memset(head,-1,sizeof(head));

    cnt=0;

    MM(d);

    MM(deg);

}

void add(int s,int t,int d)

{

    E[cnt].to=t;

    E[cnt].dx=d;

    E[cnt].pre=head[s];

    head[s]=cnt++;

}

void spfa(int s)

{

    typedef pair<int,int> pii;

    priority_queue<pii>Q;

    Q.push(pii(d[s],s));

    while (!Q.empty())

    {

        int now=Q.top().second;

        Q.pop();

        for (int i=head[now]; i!=-1; i=E[i].pre)

        {

            int v=E[i].to;

            if(d[v]>d[now]+E[i].dx)

            {

                d[v]=d[now]+E[i].dx;

                Q.push(pii(d[v],v));

            }

        }

    }

}

int main(void)

{

    int n,m,i,j,a,b,c;

    while (~scanf("%d%d",&n,&m))

    {

        init();

        for (i=0; i<m; i++)

        {

            scanf("%d%d",&a,&b);

            add(b,a,-1);

            deg[a]++;

        }

        queue<int>Q;

        int flag=0;

        for (i=1; i<=n; i++)

        {

            if(!deg[i])

            {

                Q.push(i);

                flag++;

            }

        }

        while (!Q.empty())

        {

            spfa(Q.front());

            Q.pop();

        }

        int r=0;

        for (i=1; i<=n; i++)

        {

            if(d[i]==0)

                flag--;

            r=r-d[i]+888;

        }

		flag?puts("-1"):printf("%d\n",r);

    }

    return 0;

}