#include <fstream>
#include <queue>
using namespace std;
ifstream is ("dfs.in");
ofstream os ("dfs.out");
queue <int> Q;
int n, m, a[1001][1001], viz[1001], cnt, v;
void Read();
void Conex(int x);
int main()
{
    Read();
    Conex(1);
    os << cnt;
    return 0;
}
void Read()
{
    int x, y;
    is >> n >> m;
    for(int i = 1; i <= m; ++i)
    {
        is >> x >> y;
        a[x][y] = 1;
        a[y][x] = 1;
    }
}
void Conex(int x)
{
    Q.push(x);
    viz[x] = 1;
    while(!Q.empty())
    {
        v = Q.front();
        Q.pop();
        for(int i = 1; i <= n; ++i)
        {
            if(viz[i] == 0 && a[v][i] == 1)
            {
                viz[i] = 1;
                Q.push(i);
            }
        }
    }
    cnt++;
    for(int i = 1; i <= n; ++i)
        if(!viz[i])
            Conex(i);
    return;
}