#include <fstream>

using namespace std;

ifstream f("fact.in");
ofstream d("fact.out");

int nzero(int x)
{
     int ans=0,p5=5;
     while(x>=p5)
     {
         ans+=x/p5;
         p5=p5*5;
     }
     return ans;
}

int main()
{
    int p,n=1;
    f>>p;
    while(nzero(n)<p)n++;
    if (nzero(n)==p) d << n;
    else d <<-1;
    return 0;
}