London Bridge

#include <bits/stdc++.h>

using namespace std;
using pii = pair<int,int> ;

int parent[100010];

int find(int u){
    if(parent[u]==u){
        return u;
    }
    return parent[u] = find(parent[u]);
}
int n ,m;
void merge(int u,int v){
    u=find(u);
    v=find(v);
    if(u==v){
        return;
    }
    --n;
    if(u>v){
        parent[v]=u;
    }
    else{
        parent[u]=v;
    }

}
int main(){


    scanf("%d%d",&n,&m);
    for(int i=1;i<=n;++i){
        parent[i]=i;
    }
    int u ,v;

    vector<pii> bridge;
    for(int i=1;i<=m;++i){
        scanf("%d%d",&u,&v);

        bridge.push_back(make_pair(u,v));
    }
    int cnt=0;

    for(int i=m-1;i>=0;--i){
        if(n==1){
            break;
        }
        int start=bridge[i].first;
        int end1 =bridge[i].second;
        merge(start,end1);
        ++cnt;

    }


     cout << m-cnt;
    return 0;
}