Combinations - Nested Loops

function combinations(input) {
    let n = Number(input[0]);

    let validCombinations = 0;
    for (let x1 = 0; x1 <= n; x1++) {
        for (x2 = 0; x2 <= n; x2++) {
            for (x3 = 0; x3 <= n; x3++) {

                if (x1 + x2 + x3 === n) {
                    validCombinations++;
                }
            }
        }
    }
    console.log(validCombinations);
}

combinations(["25"])