#include <iostream>
#include<fstream>
using namespace std;
ifstream f("fact.in");
ofstream g("fact.out");
int fct(int p)
{if(p<2)return -1;
if(p%5==0)return p*4+5;
int i=5;
while(p>0)
{
    int j=i;
    while(j%5==0)
    {
        p--;
        j/=5;
    }
    i+=5;
}
return i-5;
}
int main()
{int p;
f>>p;
g<<fct(p);
return 0;
}