#include <algorithm>
#include <iostream>
#include <fstream>
#include <climits>
#include <vector>
#include <stack>
#include <cmath>
// #include <bits/stdc++.h>
#define in  cin
#define out cout

using namespace std;

signed main(){
    ios_base::sync_with_stdio(false);
    in.tie(NULL);

    int p; in >> p;
    int l = 1, r = 5 * 100000000;
    int mini = 0;
    while(l <= r){
        int m = (l + r) / 2;
        int cnt = 0, pt = 5;
        for(int i = 0; i < 15; i++){
            cnt += m / pt;
            pt *= 5;
            if(pt > m) break;
        }

        // cout << "m = " << m << " Cnt = " << cnt << '\n';
        // cout << "p = " << p << '\n';
        if(cnt >= p){
            mini = m;
            r = m - 1;
        }else l = m + 1;
    }

    out << mini << '\n';

    return 0;
}