南阳28

//一个数组元素存14位，模拟即可
#include<cstdio>
int len = 0;
const long long m = 100000000000000;
long long a[10000]={1};

void solve(long long x)
{
    int add = 0;
    for(int i=0; i<=len; ++i)
    {
        a[i] *= x;
        a[i] += add;
        add = a[i]/m;
        a[i] %= m;
    }
    if(add > 0)
        a[++len] = add;
}

int main()
{
    int n;
    scanf("%d",&n);
    for(int i=n; i>0; --i)
        solve((long long)i);
    printf("%lld",a[len]);
    for(int i=len-1; i>=0; --i)
        printf("%014lld",a[i]);
    printf("
");
}