def trim(s):
    size = len(s)
    for i in range(size):
        if s[i] != ' ':
            s = s[i:]
            break
        elif size - 1 == i:
            return ''
    i = len(s) - 1;
    while (i > 0):
        if s[i] != ' ':
            s = s[:i + 1]
            break
        i = i - 1
    return s