var total_attempts = 256 * 256 * 256;
var successful_attempts = 0;
for (var a = 0; a < 256; a++) {
    for (var b = 0; b < 256; b++) {
        for (var c = 0; c < 256; c++) {
            if (a + b + c > 300)
                successful_attempts++;
        }
    }
}
console.log("Iterations: " + total_attempts);
console.log("Successful checks: " + successful_attempts);
console.log("Probability: " + (successful_attempts / total_attempts));