#include<bits/stdc++.h>
using namespace std; 
ifstream fin ("fact.in");
ofstream fout ("fact.out");
int Nr;
int num_zero (int n) {
    int aux = 5, res = 0;
    while (aux <= n) {
        res = res + n / aux;
        aux = aux * 5;
    }
    return res;
}
int cautare (int l, int r) {
    while (l <= r) {
        int m = l - (l - r) / 2;
        if (num_zero (m) < Nr)
            l = m + 1;
        else
            r = m - 1;
    }
    if (num_zero (l) == Nr)
        return l;
        else
    return -1;
}
int main () {
    fin >> Nr;
    fout << cautare (1, 5 * Nr);
    return 0;
}