#include <cstdio>
unsigned int a[20000][20000],viz[100001];
unsigned long n,m,nr=0,x,y;
void df(unsigned long s)
{for(unsigned long i=s+1;i<=n;++i)
if(!viz[i]&&a[s][i])
viz[i]=1;}
int main()
{freopen("dfs.in","r",stdin);
freopen("dfs.out","w",stdout);
scanf("%ld %ld",&n,&m);
for(unsigned long i=1;i<=n;++i)
{scanf("%ld %ld",&x,&y);
a[x][y]=a[y][x]=1;}
for(unsigned long i=1;i<=n;++i)
if(!viz[i]) 
{df(i);
++nr;}
printf("%ld",nr);
return 0;}