CodeForces

#include <cstdio>#include <cstring>#include <iostream>#include <algorithm>#include <vector>using namespace std;typedef long long ll;const int maxn = 1e5 + 10;int n, m;ll du[maxn], dp[maxn];vector<int> g[maxn];void dfs(int u) {    if (dp[u]) return;    ll temp = 0;    for (unsigned int i = 0; i < g[u].size(); i++) {        int v = g[u][i];        dfs(v);        temp = max(temp, dp[v]);    }    dp[u] = temp + 1;}int main() {    scanf("%d %d", &n, &m);    int u, v;    memset(du, 0, sizeof(du));    for (int i = 1; i <= m; i++) {        scanf("%d %d", &u, &v);        if (u < v) swap(u, v);        du[u]++; du[v]++;        g[u].push_back(v);    }    memset(dp, 0, sizeof(dp));    for (int i = 1; i <= n; i++) dfs(i);    ll ans = 0;    for (int i = 1; i <= n; i++) {        ans = max(ans, dp[i] * du[i]);    }    printf("%lld\n", ans);    return 0;}