Spanning_Tree_OF

#include <bits/stdc++.h>
#define nmax 30003
using namespace std;

vector<int> L[nmax];
int n, d[nmax];
int st[nmax], top;

void Citire()
{
    int i, j;
    cin >> n;
    while (cin >> i >> j)
    {
        L[i].push_back(j);
        L[j].push_back(i);
        d[i]++;
        d[j]++;
    }
}

void Rezolva()
{
    int i, cnt;
    for (i = 1; i <= n; i++)
        if (d[i] == 1)
            st[++top] = i;
    while (top > 0)
    {
        i = st[top--];
        for (auto j : L[i])
            if (d[j] != 1)
            {
                d[j]--;
                if (d[j] == 1)
                    st[++top] = j;
            }
    }
    cnt = 0;
    for (i = 1; i <= n; i++)
        if (d[i] > 1) cnt++;
    cout << cnt << "\n";
}

int main()
{
    Citire();
    Rezolva();
    return 0;
}