#include <fstream>
#include <iostream>

using namespace std;

ifstream fin("fact.in");
ofstream fout("fact.out");

long long p,n=1000000000;
long long nr0(long long n)
{
    long long x=0;
    while(n)
        {
            x+=n/5;
            n/=5;
            }
    return x;
}
long long cauta(long long p)
{
    long long s=1, d=n, m, N=-1;
    while(s<=d)
    {
        m=(s+d)/2;
        if(nr0(m)>=p)
        {
            N=m;
            d=m-1;
        }
        else s=m+1;
    }
    return N;
}
int main()
{
    fin>>p;
    long long  n=cauta(p);
    if(nr0(n)==p)
        fout<<n;
    else fout<<-1;
    return 0;
}