#include <fstream>

using namespace std;

long zerouri(long n,int power)
{
    if(n/power==0) return 0;
    else return n/power+zerouri(n,power*5);
}

int main()
{
    fstream f("fact.in",ios::in);
    fstream f2("fact.out",ios::out);
    long p;
    while(f>>p)
    {
    if(!p) f2<<"1\n";
    else
    {
    for(long i=5;i<=100000000;i+=5)
    {
        long z=zerouri(i,5);
        if(z==p)
        {
            f2<<i<<"\n";
            break;
        }
    }
    //long z=zerouri(p,5);
    //f<<z;
    }
    }
    f2.close();
    f.close();
    return 0;
}