高精度求N!

#include <iostream>
#include <cstdio>
#include <cmath>
#include <cstring>
using namespace std;
typedef long long LL;
const LL MOD = 100000000000000;///省时间
const int MAXN = 40000;
LL a[MAXN];
int main()
{
    int n;
    while(cin>>n)
    {
        memset(a, 0, sizeof(a));
        a[0] = 1;
        int end = 0;
        for(LL i=2; i<=n; i++)
        {
            LL c = 0;///进位
            for(LL j=0; j<=end; j++)///注意这里是个窍门
            {
                LL s = a[j]*i+c;
                a[j] = s%MOD;
                c = s/MOD;
            }
            if(c)
                a[++end] = c;
        }
        printf("%lld",a[end]);
        for(LL i=end-1; i>=0; i--)
        {
            printf("%014I64d",a[i]);
        }
        puts("");
    }
    return 0;
}