#include <fstream>
#include <iostream>
#include <algorithm>
using namespace std;
ifstream f("fact.in"); ///kruskal
ofstream g("fact.out");
int p,c,k;
int cb(int p) { /// cel mai mic nr nat n pt care n! are exact p cifre de 0
    int s=1, d=1000000000, m, pos=1, k5, c;
    while(s<=d) {
        m = s +(d-s)/2;
        c=5, k5=0; while (c<=m) k5+=m/c, c*=5;
        if (k5==p) pos=m, d = m-1;
        else if(k5>p) d=m-1;
        else s=m+1;
    }
    return pos;
}

int main()
{
    f>>p;
    g<<cb(p);
    return 0;
}