def enter():
box_len = get_box_len()
grid = Grid(box_len)
for row in range(box_len * box_len):
for col in range(box_len * box_len):
print(grid)
val = input(f'Value for ({row + 1}, {col + 1}): ') or 0
try:
val = int(val)
except ValueError:
val = ord(val.upper()) - 55
grid.get_cell(row, col).value = val
if not grid.is_valid():
print('invalid board')
exit()
return grid
