#include <iostream>
#include <vector>
#include <algorithm>
#include <map>
#include <queue>
#include <set>
#include <random>
#include <iomanip>
#include <string>
#include <cmath>
using namespace std;
typedef long long ll;
#define rep(i, n) for(int i = 0; i < (n); i++)

template<class T>
using vi = vector<T>;

template<class T>
using vii = vector<vi<T>>;

template<class T>
using viii = vector<vii<T>>;

using P = pair<ll, int>;

void chmin(ll & x, ll y) { x = min(x, y); }

int cnt(ll x) {
	int res = 0;
	while (x % 5 == 0) {
		x /= 5;
		res++;
	}
	return res;
}

int main()
{
	int n, e;
	cin >> n >> e;
	if (e == 0) {
		cout << 0 << endl;
		return 0;
	}

	int rem = ((n % 5) + 5) % 5;
	if (rem == 2 || rem == 3) {
		cout << "NaN" << endl;
		return 0;
	}

	int mx = 1 << 29;
	vi<int> cand;
	if (rem == 0) cand = { 0 };
	else if (rem == 1) cand = { 1, 4 };
	else cand = { 2, 3 };

	for (int elem : cand) {
		for (ll i = elem; i <= mx; i += 5) {
			if (i * i == n) {
				cout << i << endl;
				return 0;
			}
			int res = cnt(n - i * i);
			if (res >= e) {
				cout << i << endl;
				return 0;
			}
		}

		for (ll i = elem; i >= -mx; i -= 5) {
			if (i * i == n) {
				cout << i << endl;
				return 0;
			}
			int res = cnt(n - i * i);
			if (res >= e) {
				cout << i << endl;
				return 0;
			}
		}
	}
	cout << "NaN" << endl;
	return 0;
}