def Z_algorithm(S):
    N=len(S)
    arr = [0]*N
    arr[0] = N
    i,j = 1,0
    while i<N:
        while i+j<N and S[j]==S[i+j]:
            j += 1
        arr[i]=j
        if not j:
            i += 1
            continue
        k = 1
        while i+k<N and k+arr[k]<j:
            arr[i+k] = arr[k]
            k += 1
        i += k; j -= k
    return arr

def solve(n, a, s):
    t = []
    a = a + a
    for i in range(2 * n - 2):
        if a[i] < a[i + 1]:
            t.append('<')
        else:
            t.append('>')
    n -= 1
    t = ''.join(t)
    l = Z_algorithm(s + t)[n:]
    ans = -1
    #print(''.join(list(s + t)[n:]))
    #print(l)
    for i in range(n + 1):
        if l[i] >= n:
            ans = i
            break
    return ans


n = int(input())
a = list(map(int,input().split()))
s = input()

print(solve(n, a, s))