#pragma comment(linker, "/STACK:1024000000,1024000000")

#include <cstdio>

#include <string>

#include <cstdlib>

#include <cmath>

#include <iostream>

#include <cstring>

#include <set>

#include <queue>

#include <algorithm>

#include <vector>

#include <map>

#include <cctype>

#include <cmath>

#include <stack>

#include <sstream>

#define debug() puts("++++");

#define gcd(a, b) __gcd(a, b)

#define lson l,m,rt<<1

#define rson m+1,r,rt<<1|1

#define freopenr freopen("in.txt", "r", stdin)

#define freopenw freopen("out.txt", "w", stdout)

using namespace std;

typedef long long LL;

typedef unsigned long long ULL;

typedef pair<int, int> P;

const int INF = 0x3f3f3f3f;

const double inf = 0x3f3f3f3f3f3f;

const double PI = acos(-1.0);

const double eps = 1e-5;

const int maxn = 2000 + 10;

const int mod = 1e6;

const int dr[] = {-1, 0, 1, 0};

const int dc[] = {0, 1, 0, -1};

const char *de[] = {"0000", "0001", "0010", "0011", "0100", "0101", "0110", "0111", "1000", "1001", "1010", "1011", "1100", "1101", "1110", "1111"};

int n, m;

const int mon[] = {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};

const int monn[] = {0, 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};

inline bool is_in(int r, int c){

  return r >= 0 && r < n && c >= 0 && c < m;

}

struct Edge{

  int from, to, cap, flow;

  LL cost;

};

struct MCMF{

  int n, m;

  vector<Edge> edges;

  vector<int> G[maxn];

  int inq[maxn];

  LL d[maxn];

  int p[maxn];

  int a[maxn];

  void init(int n){

    this->n = n;

    for(int i = 0; i < n; ++i)  G[i].clear();

    edges.clear();

  }

  void addEdge(int from, int to, int cap, LL cost){

    edges.push_back((Edge){from, to, cap, 0, cost});

    edges.push_back((Edge){to, from, 0, 0, -cost});

    m = edges.size();

    G[from].push_back(m-2);

    G[to].push_back(m-1);

  }

  bool BellmanFord(int s, int t, int &flow, LL &cost){

    for(int i = 0; i < n; ++i)  d[i] = INF;

    memset(inq, 0, sizeof inq);

    d[s] = 0;  inq[s] = 1;  p[s] = 0;   a[s] = INF;

    queue<int> q;

    q.push(s);

    while(!q.empty()){

      int u = q.front();  q.pop();

      inq[u] = 0;

      for(int i = 0; i < G[u].size(); ++i){

        Edge &e = edges[G[u][i]];

        if(e.cap > e.flow && d[e.to] > d[u] + e.cost){

          d[e.to] = d[u] + e.cost;

          p[e.to] = G[u][i];

          a[e.to] = min(a[u], e.cap-e.flow);

          if(!inq[e.to])  q.push(e.to),  inq[e.to] = 1;

        }

      }

    }

    if(d[t] == INF)  return false;

    flow += a[t];

    cost += d[t] * a[t];

    int u = t;

    while(u != s){

      edges[p[u]].flow += a[t];

      edges[p[u]^1].flow -= a[t];

      u = edges[p[u]].from;

    }

    return true;

  }

  int minCost(int s, int t, LL &cost){

    int flow = 0;  cost = 0;

    while(BellmanFord(s, t, flow, cost));

    return flow;

  }

};

MCMF mcmf;

int main(){

  while(scanf("%d", &n) == 1 && n){

    mcmf.init(n+n+2);

    int v;  LL val;

    int s = 0, t = n+n+1;

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

     // mcmf.addEdge(i, i+n, 1, 0);

      mcmf.addEdge(s, i, 1, 0);

      mcmf.addEdge(i+n, t, 1, 0);

      while(scanf("%d", &v) == 1 && v){

        scanf("%lld", &val);

        mcmf.addEdge(i, v+n, 1, val);

      }

    }

    LL ans;

    if(mcmf.minCost(s, t, ans) == n)  printf("%lld\n", ans);

    else  printf("N\n");

  }

  return 0;

}