#include <iostream>
#include<fstream>
#include<climits>
using namespace std;
long long p,u,m,key;
long long zeros(long long x)
{
    long long nr=0;
    if(x==0) return -1;
    while(x!=0)
    {
        x/=5;
        nr+=x;
    }
    return nr;
}
int main()
{
    ifstream f("fact.in");
    ofstream g("fact.out");
    f>>key;
    p=0;u=LLONG_MAX;
    while(u-p>1)
    {
        m=(p+u)/2;
        if(zeros(m)<key) p=m;
        else u=m;
    }
    if(zeros(u)==key)g<<u;
    else g<<"-1";
    return 0;
}