N = int(input())
S = input()
A = list(map(int, input().split()))
B = [0] * (N + 1)
for i in range(N):
    if S[i] == "B":
        A[i] = -A[i]
    B[i + 1] = B[i] + A[i]
print(abs(max(B)-min(B)))