#include <fstream>

using namespace std;

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

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

int main()
{
    int p,n,cnt2=0,cnt5=0,START=1,END=1000000000,m,aux;
    f>>p;

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