# your code goes here
operators = ['-', '+', '*', '/']

def whitespace(s, pos):
	while s[pos] in [' ', '\n', '\t', '\r']:
		pos += 1
	return pos
	
def num(s, pos):
	buf = []
	while pos < len(s) and s[pos].isdigit():
		buf.append(s[pos])
		pos += 1
	return (''.join(buf), pos)
	
def flt(s, pos):
	n, pos = num(s, pos)
	if s[pos] == '.':
		pos += 1
		n2, pos = num(s, pos)
		return n + '.' + n2, pos
	return n, pos
	
def op(s, pos):
	if s[pos] in operators:
		pos += 1
	return pos
	
def parse(string):
	pos = whitespace(string, 0)
	num1, pos = flt(string, pos)
	pos = whitespace(string, pos)
	pos = op(string, pos)
	pos = whitespace(string, pos)
	num2, pos = flt(string, pos)
	return [num1, num2]
	
print parse("4.7 + 4.1")[1]
print parse("4.7 - 4.2")[1]
print parse("4.7 * 4.3")[1]