Problem Description
Let us consider undirected graph G = {V; E} which has N vertices and M edges. Incidence matrix of this graph is N × M matrix A = {ai,j}, such that ai,j is 1 if i-th vertex is one of the ends of j -th edge and 0 in the other case. Your task is to find the sum of all elements of the matrix ATA.
Input
The first line of the input file contains two integer numbers — N and M (2 ≤ N ≤ 10 000, 1 ≤ M ≤100 000). Then 2*M integer numbers follow, forming M pairs, each pair describes one edge of the graph. All edges are different and there are no loops (i.e. edge ends are distinct).
Output
Output the only number — the sum requested.
Sample Input
4 4 1 2 1 3 2 3 2 4
Sample Output
18
1 /* 2 * this code is made by 987690183 3 * Problem: 1213 4 * Verdict: Accepted 5 * Submission Date: 2014-10-14 13:40:27 6 * Time: 236MS 7 * Memory: 1716KB 8 */ 9 #include<iostream> 10 #include<stdio.h> 11 #include<cstring> 12 #include<cstdlib> 13 using namespace std; 14 15 int num[10002]; 16 long long get(int n,int m)/**Cn,m**/ 17 { 18 long long sum = 1; 19 for(int i=1,j=n;i<=m;i++,j--) 20 sum=sum*j/i; 21 return sum; 22 } 23 int main() 24 { 25 int n,m,x,y; 26 int hxl= 0; 27 while(scanf("%d%d",&n,&m)>0) 28 { 29 memset(num,0,sizeof(num)); 30 for(int i=1;i<=m;i++) 31 { 32 scanf("%d%d",&x,&y); 33 num[x]++; 34 num[y]++; 35 hxl = hxl+2; 36 } 37 long long tom = hxl; 38 for(int i=1;i<=10000;i++) 39 if(num[i]>=2) 40 { 41 tom=tom+get(num[i],2)*2; 42 } 43 printf("%lld\n",tom); 44 } 45 return 0; 46 }
