#include <bits/stdc++.h>
using namespace std;
const int INF = 1 << 28;
int n, m;
int f[10][320][320] = {0};
int g[2][320][320] = {0};
int old = 0, now = 1;
bool HasCircle(int b) {
  for (int i = 1; i <= n; i++) {
    for (int j = 1; j <= n; j++) {
      g[now][i][j] = -INF;
      for (int k = 1; k <= n; k++) {
        if (g[old][i][k] + f[b][k][j] > g[now][i][j]) {
          g[now][i][j] = g[old][i][k] + f[b][k][j];
        }
      }
    }
    if (g[now][i][i] > 0) {
      return true;
    }
  }
  old ^= 1;
  now ^= 1;
  return false;
}
int main() {
  cin >> n >> m;
  for (int i = 1; i <= n; i++) {
    for (int j = 1; j <= n; j++) {
      f[0][i][j] = -INF;
    }
  }
  for (int i = 1; i <= m; i++) {
    int a, b;
    cin >> a >> b;
    cin >> f[0][a][b] >> f[0][b][a];
  }
  for (int i = 1; i <= n; i++) {
    f[0][i][i] = 0;
  }
  int FL = 0;
  for (int len = 1; len <= 10; len++) {
    if ((1 << (len - 1)) > n) {
      bool flag = false;
      for (int i = 1; i <= n; i++) {
        if (f[len - 1][i][i] > 0) {
          flag = true;
        }
      }
      if (!flag) {
        cout << 0 << endl;
        return 0;
      }
      FL = len - 1;
      break;
    }
    for (int i = 1; i <= n; i++) {
      for (int j = 1; j <= n; j++) {
        f[len][i][j] = -INF;
        for (int k = 1; k <= n; k++) {
          if (f[len - 1][i][k] + f[len - 1][k][j] > f[len][i][j]) {
            f[len][i][j] = f[len - 1][i][k] + f[len - 1][k][j];
          }
        }
      }
    }
  }
  for (int i = 1; i <= n; i++) {
    for (int j = 1; j <= n; j++) {
      g[old][i][j] = -INF;
    }
  }
  for (int i = 1; i <= n; i++) {
    g[old][i][i] = 0;
  }
  int ans = 0;
  for (int len = FL - 1; len >= 0; len--) {
    if (!HasCircle(len)) {
      ans = ans + (1 << len);
    }
  }
  cout << ans + 1 << endl;
  return 0;
}
