#include <fstream>

using namespace std;
ifstream in("fact.in");
ofstream out("fact.out");
int zero(int n)
{
    int nrz=0;
    while(n>=5)
    {
        nrz+=n/5;
        n/=5;
    }
    return nrz;
}
int main()
{
    int p,n=0;
    int pas=(1<<30);
    in >> p;
    while(pas!=0)
    {
        if(zero(n+pas)<p)
            n+=pas;
        pas/=2;
    }
    out << n+1;
    return 0;
}