#include<stdio.h>
int aparitii (int n){
    int puterea,ck,k;
    puterea=0;
    ck=5;
    while (n/ck>=1){
        puterea=n/ck+puterea;
        ck=ck*5;}
    return puterea;}

int main()
{
freopen ("fact.in","r",stdin);
freopen ("fact.out","w",stdout);
int p=0,l1=0,l2,pp,n,z;
scanf ("%d",&p);
l1=1;
l2=10000000;
pp=0;
while (l1<=l2&&pp==0){
    n=(l1+l2)/2;
    z=aparitii(n);
    if (z==p){
        pp=1;
        n=n-n%5;}
    else
        if (z<p)
            l1=n+1;
    else
        l2=n-1;}
if (pp==0)
    printf ("-1");
if (p==0)
    printf ("1");
if (pp==1)
    printf ("%d",n);
return 0;
}