#include <bits/stdc++.h>

using namespace std;

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

unsigned nrdezero(int p){
    int imp = 5, cnt = 0;
    while(p >= imp){
        cnt += (p / imp);
        imp *= 5;
    }
    return cnt;
}

int main()
{
    unsigned n;
    fin >> n;
    unsigned st = 1, dr = (1 << 31);
    while(st <= dr){
        unsigned mj = (st + dr) / 2;
        unsigned ans = nrdezero(mj);
        if(ans >= n){
            dr = mj - 1;
        }
        else{
            st = mj + 1;
        }
    }
    fout << st << '\n';
    return 0;
}