#include<iostream>
#include<fstream>
using namespace std;
int p, n, c;
ifstream in("fact.in");
ofstream out("fact.out");

int fact(int x){
    int nr=0, ok=1;
    while (x%5==0){
        nr++;
        x=x/5;
    }
    return nr;
}

void numar(){
    int i=0;
    while (c<p){
        i=i+5;
        c+=fact(i);
    }
    if (c==p)
        out<<i;
    else
        out<<"-1";
}

int main(){
    in>>p;
    if (p==0)
        out<<"1";
    else
        numar();
    return 0;
}