#include <iostream>
#include <fstream>
#include <math.h>
using namespace std;
ifstream fin("fact.in");
ofstream fout("fact.out");
long long int p;
long int putere5(long long int k)
{
    long long int k1=0;
    while(k%5==0)
    {
        k=k/5;
        k1++;
    }
    return k1;
}
long long int suma(long long int p)
{
    long long int n=1,s=0;
    while(s<p)
    {
         if(n==1)
            n=n+4;
        else
            n=n+5;
        s=s+putere5(n);
    }
    if(s==p)
        return n;
    else
        return -1;
}
int main()
{

    fin>>p;
    fout<<suma(p);
    fin.close();
    fout.close();
    return 0;
}