Submission #9635

#	Time	Username	Problem	Language	Result	Execution time	Memory
9635		pichulia	Uniting (kriii2_U)	C++98	1 / 4	12 ms	3432 KiB

U

#include<stdio.h>
#define M 1000000007LL
int n;
long long int a[100009];
long long int f[100009];
long long int g[100009];
long long int s,t,u;
int main()
{
	scanf("%d",&n);
	long long int i,j, k;
	f[0] = 1;
	g[0] = 1;
	for(i=0;i<n;i++)
	{
		scanf("%lld",&a[i]);
		s = (s+a[i])%M;
		t = (t+a[i]*a[i])%M;
	}
	g[1] = 1;
	for(i=2;i<=n;i++)
	{
		g[i] = (g[i-1]*(i*(i-1)))%M;
	}
	u = (s*s-t);
	u = u/2;
	printf("%lld\n%lld\n",u,g[n]);
}

• Subtask 1: 1 / 4