#include <fstream>

using namespace std;

ifstream fin("fact.in");
ofstream fout("fact.out");

int n, p, e, x, y, ct;

int main(){
    fin>>p;
    x=5*p;
    int k=5;
    while(x>=k){
        e+=x/k;
        k*=5;
    }
    while(e>p){
        y=x;
        x-=5;
        ct=0;
        while(y%5==0){
            ct++;
            y/=5;
        }
        e-=ct;
    }
    if(e<p) fout<<-1;
    else fout<<x;

    return 0;
}