def solve_runes(runes):

    if runes[0] not in ([str(x) for x in range(10)] + ['-'] + ['?'] or ['-+', '-*'] in runes) or runes.startswith('0') or runes.startswith('-0'):
        return -1

    if runes.find('+-') != -1:
        first = runes[:runes.find('+-')]
        operation = '+'
        second = runes[runes.find('+-') + 1:runes.find('=')]
        total = runes[runes.find('=') + 1:]
    elif runes.find('*-') != -1:
        first = runes[:runes.find('*-')]
        operation = '*'
        second = runes[runes.find('*-') + 1:runes.find('=')]
        total = runes[runes.find('=') + 1:]
    elif runes.find('--') != -1:
        first = runes[:runes.find('--')]
        operation = '-'
        second = runes[runes.find('--') + 1:runes.find('=')]
        total = runes[runes.find('=') + 1:]
    elif runes.find('+') != -1:
        first = runes[:runes.find('+')]
        operation = '+'
        second = runes[runes.find('+') + 1:runes.find('=')]
        total = runes[runes.find('=') + 1:]
    elif runes.find('*') != -1:
        first = runes[:runes.find('*')]
        operation = '*'
        second = runes[runes.find('*') + 1:runes.find('=')]
        total = runes[runes.find('=') + 1:]
    elif runes.count('-') == 2:
        first = runes[:runes.rfind('-')]
        operation = '-'
        second = runes[runes.rfind('-') + 1:runes.find('=')]
        total = runes[runes.find('=') + 1:]

    for i in range(10):
        first_for = first.replace('?', str(i), first.count('?'))
        if first_for.startswith('00'):
            break
        second_for = second.replace('?', str(i), second.count('?'))
        if second_for.startswith('00'):
            break
        total_for = total.replace('?', str(i), total.count('?'))
        if total_for.startswith('00'):
            break

        if operation == '+':
            if int(first_for) + int(second_for) == int(total_for):
                return i
        elif operation == '-':
            if int(first_for) - int(second_for) == int(total_for):
                return i
        elif operation== '*':
            if int(first_for) * int(second_for) == int(total_for):
                return i
    return -1