#include <iostream>
#include <cmath>
#include <fstream>

using namespace std;

ifstream in("fact.in");
ofstream out("fact.out");
int p, n;

int Factorial(int i){
    int s = 0;
    double k = 1;
    int copie = i;

    while(i > 0){
        i = copie;
        i /= pow(5, k);
        s += i;
        ++k;
    }

    return s;

}

int main()
{
    in >> p;

    for(int i = 1; i <= p*5; ++i){
        int copie = i;
        if(Factorial(i) == p){
            n = i;
            break;
        }
    }

    if(p == 0){
        n = 1;
    }

    out << n << endl;
}