1 #include <bits/stdc++.h>
 2 #define INF 0x3f3f3f3f
 3 #define ll long long
 4 using namespace std;
 5 int n, f[300010], head[300010], num;
 6 struct node {int next, to;}stu[600010];
 7 void add(int x, int y) {stu[++num].next = head[x]; stu[num].to = y; head[x] = num; return;}
 8 int main()
 9 {
10     scanf("%d", &n);
11     for(int i = 1, x, y; i < n; ++i)
12     {
13         scanf("%d%d", &x, &y);
14         add(x, y), add(y, x);
15     }
16     ll ans = 0;
17     for(int u = 1; u <= n; ++u)
18     {
19         for(int i = head[u]; i; i = stu[i].next)
20         {
21             int x = stu[i].to;
22             if(x < u) f[u] += f[x] + 1;
23         }
24         for(int i = head[u]; i; i = stu[i].next)
25         {
26             int x = stu[i].to;
27             if(x < u) ans += (ll)(f[u] - f[x] - 1) * (f[x] + 1);
28         }
29     }
30     printf("%lld", ans);
31     return 0;
32 }

 

 

#include <bits/stdc++.h>#define INF 0x3f3f3f3f#define ll long longusing namespace std;int n, f[300010], head[300010], num;struct node {int next, to;}stu[600010];void add(int x, int y) {stu[++num].next = head[x]; stu[num].to = y; head[x] = num; return;}int main(){scanf("%d", &n);for(int i = 1, x, y; i < n; ++i){scanf("%d%d", &x, &y);add(x, y), add(y, x);}ll ans = 0;for(int u = 1; u <= n; ++u){for(int i = head[u]; i; i = stu[i].next){int x = stu[i].to;if(x < u) f[u] += f[x] + 1;}for(int i = head[u]; i; i = stu[i].next){int x = stu[i].to;if(x < u) ans += (ll)(f[u] - f[x] - 1) * (f[x] + 1);}}printf("%lld", ans);return 0;}