#include <stdio.h>
using namespace std;
int p;
int cp(int p)
{
    int aux=1,i;
    for (i=1; i<=p; i++) aux*=5;
    return aux;
}
int zerouri(int nr){
    int c=0,i,aux;
    c= nr /5;
    i=2;
    while (cp(i)<=nr){c+=i-1; i++;}
    return c;

}
int main(){
    int z=0, a,b,aux; bool gasit=false;
    freopen("fact.in","r",stdin);
    freopen("fact.out","w",stdout);
    scanf("%d", &p);
    a=0;
    b=100000000;
    while ((a<=b) && (!gasit))
    {

        aux=(a+b) /2;
        z = zerouri(aux);

        if (z>p) {b=aux-1;}
        else if (z<p) {a=aux+1;}
        else gasit=true;
    }
    while(zerouri(aux-1)==p) aux--;
    if (p==0) printf("1");
    else if (gasit) printf("%d",aux);
    else printf("-1");


    return 0;
}