from itertools import pairwise


def rolling_hash(s: str):
    """[l, r] のハッシュを返す関数を返す"""
    mod = 998244353
    p = 1009
    n = len(s)
    t = [ord(c) for c in s]
    a = [0] * n
    b = [0] * n
    a[0] = t[0]
    b[0] = 1
    for i in range(1, n):
        a[i] = (a[i-1] * p + t[i]) % mod
        b[i] = (p * b[i-1]) % mod

    # [l, r] のハッシュ値
    def f(l: int, r: int) -> int:
        assert 0 <= l <= r < n
        h = a[r]
        if l > 0:
            h -= a[l-1] * b[r-l+1]
            h %= mod
        return h

    return f


N = int(input())
A = list(map(int, input().split()))
S = input()

cs = []
for a, b in pairwise(A + A):
    if a < b:
        cs.append('<')
    else:
        cs.append('>')

rh = rolling_hash(''.join(cs))
h = rolling_hash(S)(0, len(S)-1)
for i in range(N):
    if rh(i, i+len(S)-1) == h:
        print(i)
        break
else:
    print(-1)