#include <cstdio>
#include <vector>
#include <algorithm>
using namespace std;

vector<int> vecini[100005];
int vizitat[200005];
int n,m,x,y;

void dfs(int k){
    if(vizitat[k] == 0){

        vizitat[k] = 1;

        for(int i = 0; i < vecini[k].size(); i++){
            dfs(vecini[k][i]);
        }
    }
}
int main()
{
    freopen("dfs.in","r",stdin);
    freopen("dfs.out","w",stdout);
    scanf("%d %d",&n,&m);
    for(int i = 1; i <= m; i++){
        scanf("%d %d",&x,&y);
        vecini[x].push_back(y);
        vecini[y].push_back(x);
    }
    int ok = 0;
    int i = 1,total = 0;

    while(ok == 0){
        total++;

        dfs(i);

        int da = 1;
        for(int j = i; j <= n; j++){
            if(vizitat[j] == 0){
                i = j;
                da = 0;
                break;
            }
        }
        if(da == 1)
            ok = 1;
    }
    printf("%d",total);
    return 0;
}