求大数阶乘

#include <iostream>
using namespace std;
int main()
{
    int a[1000];
    int digit,n;
    cin>>n;
    a[0]=1;
    digit=1;
    for(int i=2;i<=n;i++){
        int num=0;
        for(int j=0;j<digit;j++){
            int tmp = a[j]*i+num;
            a[j] = tmp%10;
            num = tmp/10;
        }
        while(num){
            a[digit] = num%10;
            num = num/10;
            digit++;
        }
    }
    for(int i = digit-1;i>=0;i--){
        cout<<a[i];
    }
    cout<<endl;
    return 0;
}