#739. Add, subtract, add...

when green flag clicked
set [i v] to (0)
set [s v] to (0)
repeat (3)
change [i v] by (1)
if <((i) mod (2)) = (0)> then
change [s v] by (i)
else
change [s v] by ((0) - (i))
end
end

# When the green flag is clicked
i = 0
s = 0
for _ in range(3):
    i += 1
    if (i % 2) == 0:
        s += i
    else:
        s += 0 - i

// Scratch's mod gives a positive remainder even for negative numbers
function mod(a, b) {
  return ((a % b) + b) % b;
}

let i = 0, s = 0;

// When the green flag is clicked
i = 0;
s = 0;
for (let j = 0; j < 3; j++) {
  i += 1;
  if ((mod(i, 2)) === 0) {
    s += i;
  } else {
    s += 0 - i;
  }
}

💡 Not sure? Build it in Scratch and try it out.