#include<iostream>
#include<fstream>
#include<vector>
using namespace std;
long long  n;
ifstream in("fact.in");
ofstream out("fact.out");
long long  nrcifr(long n)
{
     long long  f=0;
    for(long long  i=5;i<=n;i=i*i)
        f=n/i+f;
    return f;
}
long long cauarebinara0(long long k)
{
    long long  step=2<<27;
    long long  sol=0;
    for(; step>=1; step=step/2)
       if(nrcifr(step+sol)<k)
          sol=step+sol;
    return sol+1;
}
int main()
{
    in>>n;
    long long f =cauarebinara0(n);
    if(nrcifr(f)==n)
        out<<f;
    else
        out<<"-1";
}