#include <fstream>

using namespace std;

ifstream f("factorial.in");
ofstream g("factorial.out");

int zero(int nr)
{
    int cnt=0, i;
    for(int i=5;i<=nr;i*=5){
        cnt+=nr/i;
    }
    return cnt;
}

int main()
{
    int p,n,start=1,end=500000000,m,aux;
    f>>p;

    while(start<=end)
    {
        m=(start+end)/2;
        if(zero(m)<p)
        {
            start=m+1;
        } else {
            end = m-1;
        }
    }
    if(zero(start)==p){
        g<<start;
    } else {
        g<<"-1";
    }
    return 0;
}