#include <stdio.h>#include <stdlib.h>#include <string.h>#include <math.h>#include <limits.h>#include <ctype.h>#include <assert.h>#include <iostream>#include <iomanip>#include <sstream>#include <algorithm>#include <vector>#include <queue>#include <set>#include <map>#include <stack>#include <deque>#include <list>using namespace std;typedef long long ll;typedef unsigned long long ull;typedef pair<ll, ll> pll;typedef pair<int, int> ii;typedef vector<int> vi;typedef vector<ii> vii;typedef char C;typedef string S;const double PI = 2.0 * acos(0.0);#define gcd(a,b) __gcd(a,b)#define clr(a) memset(a, 0, sizeof(a))#define mem(a,b) memset(a, b, sizeof(a))#define REP(i, a, n) for(int i = a; i < n; ++i)#define RREP(i, a, n) for(int i = a; i > n; --i)#define REPE(i, a, n) for(int i = a; i <= n; ++i)#define RREPE(i, a, n) for(int i = a; i >= n; --i)#define fr first#define sc second#define pb push_back#define pp pop_back#define mp make_pair#define IT iterator#define all(v) v.begin(), v.end()#define ssort(v) stable_sort(v.begin(), v.end())#define LB(v, x) lower_bound(v.begin(), v.end(), x)#define UB(v, x) upper_bound(v.begin(), v.end(), x)#define loop(i, x) for(__typeof((x).begin()) i=(x.begin()); i!=(x).end(); ++i)#define rloop(i, x) for(__typeof((x).rbegin()) i=(x.rbegin()); i!=(x).rend(); ++i)#define sz(a) (int)a.size()#define sf scanf#define pf printf#define NL pf("n")#define sf1(a) scanf("%d",&a)#define sf2(a,b) scanf("%d %d",&a,&b)#define sf3(a,b,c) scanf("%d %d %d", &a,&b, &c);#define sf4(a,b,c,d) scanf("%d%d%d%d",&a,&b,&c,&d);#define oo 1000000000#define MOD 1000007#define M 100099int cases = 1;bool vis[510];bool g[510][510];int par[510];int n;void floyd_warshall(void){ REPE(k,1,n) REPE(i,1,n) REPE(j,1,n) if(g[i][k] && g[k][j]) g[i][j] = true; return ;}bool dfs(int u){ REPE(i,1,n) { if(vis[i] == 0 && g[u][i] == true) { vis[i] = true; if(par[i] == -1 || dfs(par[i])) { par[i] = u; return true; } } } return 0;}int hungary(void){ mem(par,-1); int ret = 0; REPE(i,1,n) { mem(vis,0); ret += dfs(i); } return ret;}int main(){ int test,m,u,v; while(sf2(n,m) == 2 && n) { mem(g,0); while(m--) { sf2(u,v); g[u][v] = true; } floyd_warshall(); int ans = n-hungary(); pf("%dn",ans); } return 0;}
