[5]INT arr = 0;
assert arr[1] == 0;
arr[0] = 100;
assert arr[0] == 100;
arr[1] = 200;
assert arr[1] == 200;
assert arr[1][10?] == 200;
arr[2?][3?] = 300;
assert arr[2] == 300;
assert arr[2?] == 300;
assert arr[2][10?] == 300;
assert arr[2?][5?] == 300;