##############################################
# The goal for this exercise is to implement
# a Terrace class that allows the main program
# below to successfully solve the
# Hanging Out on the Terrace contest problem
# (see open.kattis.com/problems/hangingout)
##############################################


##############################################
# implement a Terrace class here that supports:
#  - constructor that accepts terrace capacity as parameter
#  - processEnter(n) function to model arrival of n people
#  - processLeave(n) function to model departure of n people
#  - getNumDenied() function that returns total number of GROUPS
#                   thus far denied during the simulation
##############################################

class Terrace:
    pass




##############################################
# Do not change anything below this line
##############################################

limit,n = [int(k) for k in input().split()]
terrace = Terrace(limit)
for _ in range(n):
    pieces = input().split()
    j = int(pieces[1])
    if pieces[0] == 'enter':
        terrace.processEnter(j)
    else:
        terrace.processLeave(j)

print(terrace.getNumDenied())