#include<cstdio>

 #include<cstring>

 #include<iostream>

 using namespace std;

 int match[], vis[], g[][], n;

 inline int dfs(int u){

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

         if(g[u][i] && !vis[i]){

             vis[i] = ;

             if(!match[i] || dfs(match[i])){

                 match[i] = u;

                 return ;

             }

         }

     }

     return ;

 }//匈牙利

 inline int hungary(){

     int ans = ;

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

         memset(vis, , sizeof(vis));

         if(dfs(i)) ans++;

     }

     return ans;

 }

 int main(){

     int k;

     while(~scanf("%d%d", &n, &k)){

         for(int i = ; i <= k; i++){

             int r, c;

             scanf("%d%d", &r, &c);

             g[r][c] = ;

         }

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

     }

     return ;

 }