function assert(a) {
    if (!a)
        throw new Error("Bad assertion");
}

assert.sameValue = function (input, expected, message) {
    if (input !== expected)
        throw new Error(message);
}

function testAdd(x, y, z) {
    assert.sameValue(x + y, z, x + " + " + y + " = " + z);
    assert.sameValue(y + x, z, y + " + " + x + " = " + z);
}

let o = {
    [Symbol.toPrimitive]: function () { return 300000000000000n; }
}

testAdd(500000000000438n, o, 800000000000438n);

o.valueOf = function () {
    throw new Error("Should never execute it");
};

testAdd(700000000000438n, o, 1000000000000438n);

o.toString = function () {
    throw new Error("Should never execute it");
};

testAdd(700000000000438n, o, 1000000000000438n);

delete o.valueOf;

testAdd(700000000000438n, o, 1000000000000438n);