#include <bits/stdc++.h>
using namespace std;
#define int long long
 
signed main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
 
    long long h, d;
    cin >> h >> d;
 
    // Tìm k sao cho k*(k+1)/2 <= h
    long long k = (sqrt(8.0*h + 1) - 1) / 2;
 
    // Nếu chạy liên tiếp đủ để vượt d
    if (k >= d) {
        cout << d << "\n";
        return 0;
    }
 
    // Tính thể lực còn lại sau khi chạy k bước
    long long used = k*(k+1)/2; 
    long long remain = h - used;
 
    // Số bước cần chạy thêm
    long long need = d - k;
 
    // Khi chạy tiếp bước (k+1), cần (k+1) thể lực.
    // Nếu thiếu, phải nghỉ thêm.
    long long nextCost = k + 1;
 
    long long restNeeded = 0;
    if (remain < nextCost) {
        restNeeded = nextCost - remain;
        remain = nextCost;   // Sau khi nghỉ xong, đủ để chạy bước này
    }
 
    // Tổng lượt = số lượt đã chạy k + lượt nghỉ + lượt chạy thêm cần
    long long result = k + restNeeded + need;
 
    cout << result << "\n";
    return 0;
}
 

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