def evaluate_expression(expression):
    if expression[0] == 'f':
        return expression[-1]
    if len(expression) == 5:
        if expression[0] == 't':
            return expression[2]

    shorter_expression = expression[2:-2]
    return evaluate_expression(shorter_expression)



input_str = input()
expression = input_str.replace(" ", "")
result = evaluate_expression(expression)
print(result)