源码：

#include<cstdio>

int main()

{

const int MOD=1000000;

int i,j,n,S=0;

scanf("%d",&n);

if(n>25) n=25;//25后末尾都是6个0

for(i=1;i<=n;i++){

int factorial=1;

for(j=1;j<=i;j++)

factorial=factorial*j%MOD;

S=(S+factorial)%MOD;

}

printf("%d",S);

return 0;

}