int program (int argc, string[] argv) {
  var gas = new int[]{1,2,3,4,5};
  var costs = new int[]{3,4,5,1,2};
  var size = 5;
  var index = can_complete(gas, costs, size);
  return index;
}

int can_complete(int[] gas, int[] costs, int size) {
  var curr = 0;
  var total = 0;
  var diff = 0;
  var startIdx = 0;

  for (var i = 0; i < size; i = i + 1;) {
    diff = gas[i] - costs[i];
    total = total + diff;
    curr = curr + diff;

    if (curr < 0) {
      startIdx = i + 1;
      curr = 0;
    }
  }

  if (total >= 0) {
    return startIdx;
  }

  return -1;
}