input()
A = [int(x) if s == "R" else int(x) * (-1) for s, x in zip(input(), input().split())]


val = 0
min_val = 0
max_val = 0
res = 0
for x in A:
    val += x
    res = max(res, abs(val - min_val))
    res = max(res, abs(val - max_val))
    min_val = min(min_val, val)
    max_val = max(max_val, val)

print(res)