这是代码

#include<stdio.h>
long long int summation(int a, int b);
int main(void){
	int n;
	scanf("%d",&n);
	int i = n;
	int j = n;
	long long int m;
	while(j > 0){
		i = j;
		m = m + summation(i, n);
		j --;	
	}
	printf("%d",m);
	return 0;
}

long long int summation(int a, int b){
		long long int sum = 1;	
		for(; a > 0; a --){
		sum = sum * a;
	}
	return sum;
}

谢谢大家辽