#include <iostream>
#include <fstream>
#define NMax 100000001
using namespace std;
ifstream f("fact.in");
ofstream g("fact.out");
int fct (int x)
{
    int a=5,rez=0;
    while (x/a)
    {
        rez=rez+x/a;
        a=a*5;
    }
    return rez;
}
int main ()
{
    int p;
    f>>p;
    if (p==0) g<<1;
    else
    {
        int min=1,max=NMax,mid;
        bool ok=false;
        while (min<=max && !ok)
        {
            mid=min+(max-min)/2;
            if (fct(mid)<p) min=mid;
            else if (fct(mid)>p) max=mid;
            else ok=true;
        }
        if (ok)
        {
            while (mid%5) mid--;
            g<<mid;
        }
        else g<<-1;
    }
}