#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
#include <iostream>
using namespace std;

using lint = long long;

int dist(lint x) {
    if (x == 0) return 100;
    int ret = 0;
    while (x % 5 == 0) x /= 5, ret++;
    return ret;
}

int main() {
    int N, E;
    cin >> N >> E;

    lint ret = -1;
    for (int current = 0; current <= (1 << 29); ++current) {
        if (dist(lint(current) * current - N) >= E) {
            ret = current;
            break;
        }
    }

    // assert(ret <= (1 << 29));
    if (ret >= 0) {
        cout << ret << endl;
    } else {
        puts("NaN");
    }
}