第一题
n, m = map(int, input().split())
dp = [-1] * (m + 1)
for j in range(m + 1):
dp[j] = -1
dp[0] = 0
for i in range(1, n + 1):
s = input()
if s == "b":
type = int(input())
t = dp[type]
dp[type] = max(dp[0], dp[type])
else:
type, v = map(int, input().split())
if dp[type] != -1:
dp[0] = max(dp[0], dp[type] + v)
res = max(dp)
print(res)