let mut rel_bord_0 = [0u8; NUM_ENVELOPES];
let mut rel_bord_1 = [0u8; NUM_ENVELOPES];
for el in rel_bord_0[..num_rel_0].iter_mut() {
let mut rel_bord_0 = [0u8; NUM_ENVELOPES];
let mut rel_bord_1 = [0u8; NUM_ENVELOPES];
for el in rel_bord_0[..num_rel_0].iter_mut() {