Well Predicted

// The array is sorted beforehand
for (auto i = 0u; i < arr.size(); ++i) {
  if (arr[i] > 128)
    sum += arr[i];
}

int sum[2] = {0, 0};
for (auto i = 0u; i < arr.size(); ++i) {
  sum[arr[i] > 128] += arr[i];
}
// The answer is in sum[true]