n = int(input())

num = 0
changed = False
changedNum = 0
for i in range(0, 2 * n):
    command = input()
    if command == 'remove':
        num -= 1
        if changed:
            changedNum += 1
            changed = False
    else:
        boxNum = int(command.split(' ')[1])
        if num == 0:
            minNum = boxNum

        if boxNum > minNum:
            changed = True

        num += 1

print(changedNum)