#include <iostream>
using namespace std;
#include <vector>
#define vi vector<int>
#define ll long long
#include <algorithm>
#include <set>
#include <string>
#include <bitset>
#include <cmath>
#include <math.h>
#define pll pair<ll,ll>
#define vll vector<ll>
#define pi pair<int,int>
#include <map>
#include <queue>
#define pd pair<double,double>
#include <stack>
const int siz = 1e5 + 1;
int c[siz];
vi fr[siz];
bool vis[siz];
int pad[siz];
vi frt[siz];
ll w[siz];
int sor[siz];
int cum[siz];
void dfs(int i, int so) {
if (vis[i])return;
sor[i] = so;
cum[so]++;
vis[i] = 1;
for (int f : fr[i]) {
if (!vis[f]) {
pad[f] = i;
dfs(f,so);
}
else if (f != pad[i] && c[i]==i) {
int k = pad[i];
while (k != f) {
w[i]++;
c[k] = i;
k = pad[k];
}
w[i]++;
c[k] = i;
}
}
}
ll ans = 0;
int n, m;
bool vist[siz];
int dfst(int i, int t) {
if (vist[i])return;
vist[i] = 1;
vll v;
int sum = w[i];
for (int f : frt[i]) {
if (!vist[f]) {
v.push_back(dfst(f,t));
sum += v.back();
}
}
v.push_back(t - sum);
ans += (w[i] * (t - 1)) * (t - 2);
for (ll k : v) {
ans -= w[i] * k * (k - 1);
ans -= k * 2 * (w[i] - 1);
}
return sum;
}
int main()
{
cin >> n >> m;
for (int i = 0; i < m; i++) {
int a, b;
cin >> a >> b;
a--, b--;
fr[a].push_back(b);
fr[b].push_back(a);
}
for (int i = 0; i < n; i++) {
w[i] = 1;
c[i] = i;
}
for (int i = 0; i < n; i++) {
if (!vis[i]) {
pad[i] = i;
dfs(i,i);
}
}
for (int i = 0; i < n; i++) {
for (int f : fr[i]) {
if (c[i] != c[f]) {
frt[c[i]].push_back(c[f]);
}
}
}
for(int i = 0; i < n; i++)if(!vist[c[i]])dfst(c[i],cum[sor[i]]);
cout << ans;
}
/*
4 3
1 2
2 3
3 4
*/
Compilation message
count_triplets.cpp: In function 'int dfst(int, int)':
count_triplets.cpp:55:17: error: return-statement with no value, in function returning 'int' [-fpermissive]
55 | if (vist[i])return;
| ^~~~~~
