Codeforces 14D

#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
const int MAX = 205;
int dep, n, map[MAX][MAX];
int dfs(int u, int v){
    int max1, max2, path_max;
    max1 = max2 = path_max = 0;
    for(int i = 1;i <= n;i ++){
        if(map[i][u] && i != v){
            int z = dfs(i, u);
            if(path_max < z) path_max = z;
            if(max1 < dep){
                max2 = max1;
                max1 = dep;
            }
            else if(max2 < dep) max2 = dep;
        }
    }
    if(path_max < max1 + max2) path_max = max2 + max1;
    dep = max1 + 1;
    return path_max;
}

int main(int argc, char const *argv[]){
    int u, v;
    //freopen("in.c", "r", stdin);
    while(~scanf("%d", &n)){
        memset(map, 0, sizeof(map));
        for(int i = 0; i < n - 1;i ++){
            scanf("%d%d", &u, &v);
            map[u][v] = map[v][u] = 1;
        }
        int ans = -1;
        for(int i = 1;i <= n;i ++){
            for(int j = 1;j <= n;j ++){
                if(map[i][j]){
                    int a = dfs(i, j);
                    int b = dfs(j, i);
                    ans = max(ans, a*b);
                }
            }
        }
        printf("%d
", ans);
    }
    return 0;
}