#include <cstdio>
using namespace std;
int v[100000],a,b,m,n,NrCon,i;
int main()
{
    freopen("DFS.in","r",stdin);
    freopen("DFS.out","w",stdout);
    scanf("%d%d",&n,&m);
    NrCon=n-m;
    for(i=1;i<=m;i++)
    {
        scanf("%d%d",&a,&b);
        if(v[a]==0)
        {v[a]=NrCon+1;
        v[b]=v[a];
        }
        else
        {
            v[b]=v[a];
        }
    }
    printf("%d",NrCon);
    return 0;
}