function luckBalance(k, contests) {
    // Write your code here
    const unimportantArr = contests.filter(c => c[1] === 0);
    const importantArr = contests.filter(c => c[1] === 1);
    // sort -> from least important to max important
    importantArr.sort((a, b) => a[0] - b[0] < 0 ? 1 : -1);
    
    // we lose all unimportant constests for max luck
    const luckU = unimportantArr.reduce((a, c) => a + c[0] , 0);
    // the least important ones (lower than k) we win, else we lose to gain luck
    const luckI = importantArr.reduce(
        (a, c, idx) => idx >= k ? a - c[0] : a + c[0], 0);
    
    return luckU + luckI;
}