#include <bits/stdc++.h> using namespace std; #define MAXN 300005 #define pb push_back typedef long long lld; int N, M, C; int dep[MAXN]; int U[MAXN], D[MAXN], F[MAXN]; vector <int> con[MAXN], child[MAXN]; void dfs(int n, int from) { for (int t: con[n]) if (t != from){ if (!dep[t]){ child[n].pb(t); dep[t] = dep[n]+1; int tmp = U[n]; dfs(t, n); F[t] = U[n]-tmp; U[n] += U[t]; D[n] += D[t]; }else if (dep[t] < dep[n]){ D[n]++; U[t]++; } } } int main() { scanf("%d%d", &N, &M); for (int i=1;i<=M;i++){ int a, b; scanf("%d%d", &a, &b); con[a].pb(b); con[b].pb(a); } dep[1] = 1; dfs(1, 0); lld ans = 0; for (int i=1;i<=N;i++){ bool skip = 0; for (int t: child[i]) if (D[t]-F[t] > 1 || U[t]) skip = 1; if (skip || M-(N-1)-D[i] != 0) continue; ans += i; } printf("%lld\n", ans); }

cat.cpp: In function 'int main()':
cat.cpp:24:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d%d", &N, &M);
     ~~~~~^~~~~~~~~~~~~~~~
cat.cpp:26:24: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         int a, b; scanf("%d%d", &a, &b);
                   ~~~~~^~~~~~~~~~~~~~~~