poj 2545 Hamming Problem

#include <iostream>
using namespace std;
long long  prime[100000000];
int start[3];
int main()
{
    int factor[3],n,j;long long i,min;
    cin>>factor[0]>>factor[1]>>factor[2]>>n;
    prime[0]=1;
    for(i=1;i<=n;i++)
    {
        min=1000000000000000000;
        for(j=0;j<3;j++)
            if(prime[start[j]]*factor[j]<min)
                min=prime[start[j]]*factor[j];
        prime[i]=min;
        for(j=0;j<3;j++)
            if(prime[start[j]]*factor[j]==min)
                start[j]++;
    }
    cout<<prime[n]<<endl;
    return 0;
}