Cod sursa(job #885128)
#include<cstdio>
#include<vector>
using namespace std;
#define mata vector<int>
int n,m;
mata v[100002];
mata::iterator it;
void list(void){
int i,x,y;
for(i=0;i<m;++i){
scanf("%d%d",&x,&y);
v[x].push_back(y); v[y].push_back(x);
}
}
bool found(int where,int tofind){
for(it=v[where].begin();it!=v[where].end();++it)
if(*it==tofind) return 1;
return 0;
}
void df(int nod,int viz[]){
int i;
viz[nod]=1;
for(i=1;i<=n;++i)
if(!viz[i]&&found(nod,i)) df(i,viz);
}
int main(){
int i,viz[100002]={0},cont=0;
freopen("dfs.in","r",stdin);
freopen("dfs.out","w",stdout);
scanf("%d%d",&n,&m);
list();
for(i=1;i<=n;++i)
if(!viz[i]){
df(i,viz);
++cont;
}
printf("%d\n",cont);
return 0;
}