rows = '12345678'
cols =  'ABCDEFGH'

#class vec2:
#    def __init__(self, x, y):
#        self.x = int(x)
#        self.y = int(y)
#    def __add__(self, other):
#        return vec2(self.x + other.x, self.y + other.y)
#    def __sub__(self, other):
#        return vec2(self.x - other.x, self.y - other.y)
#    def __mul__(self, scalar):
#        return vec2(self.x * scalar, self.y * scalar)
#    def __repr__(self):
#        return 'vec2({},{})'.format(self.x, self.y)
#    def __eq__(self, other):
#        return self.x == other.x and self.y == other.y

class vec2:
    def __init__(self, x, y):
        x, y = int(x), int(y)
#        if not 0 <= x < 8:
#            raise Exception('invalid chessvec x: {}'.format(repr(x)))
#        if not 0 <= y < 8:
#            raise Exception('invalid chessvec y: {}'.format(repr(y)))
        self.x = x
        self.y = y
    def __add__(self, other): # Add vec2
        return vec2(self.x + other.x, self.y + other.y)
    def __sub__(self, other): # Subtract vec2
        return vec2(self.x - other.x, self.y - other.y)
    def __eq__(self, other):
        return self.x == other.x and self.y == other.y
    def __hash__(self):
        return hash(self.x) + hash(self.y)
    def __repr__(self):
        return 'vec2({},{})'.format(self.x, self.y)
    def __str__(self):
        return cols[self.x] + rows[self.y] if self.is_valid() else repr(self)
    def is_valid(self):
        return 0 <= self.x < 8 and 0 <= self.y < 8

def vec2_from_text(s):
    return vec2(cols.index(s[0]), rows.index(s[1]))