N: 8
SIDE: 40
MARGIN: 5
BLACK: |0|
WHITE: |255|
GRAY: |128|
---
dimension: (N * SIDE + MARGIN * 2,N * SIDE + MARGIN * 2)
background: GRAY
---
setlinecolor BLACK
for l in [0, N[ {
  for c in [0, N[ {
    if ((l + c) % 2 == 0) {
      setfillcolor WHITE
    } else {
      setfillcolor BLACK
    }
    square (c * SIDE + MARGIN,l * SIDE + MARGIN), SIDE
  }
}