1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
#include <iostream>
#include <vector>

using namespace std;

vector<vector<int>> map(101, vector<int>(101));
vector<bool> visit(101);
int cont;
int N, M;
void dfs(int s){
    cont++;
    visit[s] = true;
    for(int i = 1; i<=N; i++){
        if(map[s][i] == 1 && visit[i] == false) dfs(i);
    }
}
int main(){
    
    scanf("%d", &N);
    scanf("%d", &M);
    
    for(int i = 0; i<M; i++){
        int start;
        int end;
        scanf("%d %d", &start, &end);
        map[start][end] = 1;
        map[end][start] = 1;
    }
    
    dfs(1);
    printf("%d\n", cont-1);
}