#include <fstream>

using namespace std;

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

int cant(int a)
{
    int can=0;
    while(a%5==0)
    {
        a/=5;
        can++;
    }
    return can;
}

int main()
{
    int p,fact=0;
    in>>p;
    int i=0;
    if(p>1){
        while(fact<p){
            i+=5;
            fact+=cant(i);
        }
        ///if(fact==p)
        out<<i;
        ///else out<<-1;
    }
    else out<<1;
    return 0;
}