
#add imlemenatation
def add(x,y):
    return x+y
# subtract imlemenatation
def subtract(x,y):

    if y>x:
		return ERROR
	else:
		return x-y
 
# multiply imlemenatation
def multiply(x,y):
    return x*y
#divide imlemenatation
def divide(x,y):
    return x/y