#include <bits/stdc++.h>
using namespace std;
using ll = long long;

int main(){
    ll n, m;
    cin >> n >> m;
    if(n == 1){
        cout << "NaN\n";
        return 0;
    }
    long double sq = sqrtl(n);
    ll ans = 0, v = 20 * m;
    for(int i = 0; i <= v; i++){
        ll l = i * sq;
        ll r = (i + 1) * sq;
        ans = l + 1;
        while(m >= 1 && ans < r){
            m--;
            if(m == 0){
                cout << ans << '\n';
                return 0;
            }
            ans++;
        }
    }
    assert(false);
}