for (var i = 0; i < 20000000; ++i) {
    var result = i + 1;
    result += i + 2;
    result += i + 3;
    result += i + 4;
    result += i + 5;
    result += i + 6;
    result += i + 7;
    if (result != i * 7 + 28)
        throw "Error: bad result at iteration " + i + " : " + result;

}