#include <fstream>
using namespace std;

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

int r;


int main()
{
    f>>r;
    int q=500000000, p=1, m, ok=0;
    while(p<q)
    {
        m=p+(q-p)/2;
        int nr=0;
        int pr=5;
        while(pr<m) nr=nr+m/pr, pr*=5;
        if(nr==r) p=m, q=m;
        else if(nr<r) p=m+1;
        else q=m-1;
    }
    m=p+(q-p)/2;
    int nr=0;
    int pr=5;
    while(m/pr) nr=nr+m/pr, pr*=5;
    if(nr==r) ok=m;
    else if(nr<r) p=m+1;
    else q=m-1;
    if(ok<5) g<<-1<<"\n";
    else g<<ok-ok%5;
    return 0;
}