#include <iostream>
#include <fstream>
using namespace std;
ifstream f("fact.in");
ofstream g("fact.out");
int n,p;
int main()
{
    int i;
    f>>p;
    for(i=5;p>0;i=i+5)
    {
        int cop=i;
        while(cop%5==0)
        {
            p--;
            cop=cop/5;
        }

    }
    if(i==5&&p==0)
        i=6;
    if(p<0)
        g<<"-1";
    else
        g<<i-5;
    return 0;
}