//#include <iostream>
#include <fstream>
using namespace std;
ifstream cin ("fact.in");
ofstream cout ("fact.out");
int noOfZeros (int a)
{
    int p=5, s=0;
    while (p <= a)
        s += a/p, p*=5;

    return s;
}
int main()
{
    int n;
    cin >> n;

    long long s=1, d=1000000000, mid, last;
    while (s <= d)
    {
        mid = (s+d)/2;
        if (noOfZeros(mid) >= n) {
            d = mid-1;
            last = mid;
        }
        else if (noOfZeros(mid) < n)
            s = mid+1;
    }
    cout << last;
    return 0;
}