hdu1018 big number

Problem : 1018 ( Big Number )     Judge Status : Accepted
RunId : 5383214    Language : G++    Author : billforum
Code Render Status : Rendered By HDOJ G++ Code Render Version 0.01 Beta
#include <iostream>
#include <cmath>
using namespace std;

int main()
{
    int n, num;
    cin >> n;
    for(int i=0;i<n; i++)
    {
        cin >> num;
        if(num == 1)
        {
            cout <<"1"<< endl;
            continue;
        }
        double sum = 0.0;
        for(int j=1; j<=num; j++)
        {
            sum+=log10(double(j));
        }
        cout <<(int)sum+1<< endl;
    }
    return 0;
}