#include <iostream>
#include <fstream>
using namespace std;
ifstream fin("fact.in");
ofstream fout("fact.out");
long long int p;
int putere5(long long int k)
{
    int k1=1;
    k=k/5;
    while(k%5==0)
    {
        k1++;
        k=k/5;
    }
    return k1;
}
int main()
{

    fin>>p;
    long long int i,n=0,p1=5*p;
    if(p==0)
        fout<<1;
    else
    {
        for(i=5;i<=p1&&n<p;i=i+5)
         n=n+putere5(i);
         if(n==p)
            fout<<i-5;
            else
                fout<<-1;
         }

    fin.close();
    fout.close();
    return 0;
}