#include <bits/stdc++.h> using namespace std; int n, m, a, b, f[105][105], ans[105]; int main() { cin >> n >> m; for (int i = 1; i <= n; i++) { for (int j = 1; j <= n; j++) { f[i][j] = i == j ? 0 : 0x3f3f3f3f; } } for (int i = 1; i <= m; i++) { cin >> a >> b; f[a][b] = 1; } for (int k = 1; k <= n; k++) { for (int i = 1; i <= n; i++) { for (int j = 1; j <= n; j++) { f[i][j] = min(f[i][j], f[i][k] + f[k][j]); } } } for (int i = 1; i <= n; i++) { for (int j = 1; j <= n; j++) { if (f[i][j] != 0x3f3f3f3f && f[i][j] > 0) { ans[i]++; ans[j]++; } } } for (int i = 1; i <= n; i++) { if (ans[i] == n - 1) { ans[0]++; } } cout << ans[0] << endl; return 0; }