#include <iostream>
#include <fstream>
#include <algorithm>
using namespace std;
int p,cnt,x,i,aux;
int main(){
    ifstream fin("fact.in");
    ofstream fout("fact.out");
    fin>>p;
    if(p!=0){
        while(cnt<p){
            i++; aux=i;
            while(aux%5==0){
                cnt++;
                aux/=5;
            }
            cnt++;
        }
        x=i*5;
        fout<<x;
    } else{
        fout<<1;
    }
    fin.close();
    fout.close();
    return 0;
}