import sys
#input = sys.stdin.readline
#input = sys.stdin.buffer.readline #文字列はダメ
#sys.setrecursionlimit(1000000)
#import bisect
#import itertools
#import random
#from heapq import heapify, heappop, heappush
#from collections import defaultdict 
#from collections import deque
#import copy
#import math
#from functools import lru_cache
#@lru_cache(maxsize=None)
#MOD = pow(10,9) + 7
#MOD = 998244353
#dx = [1,0,-1,0]
#dy = [0,1,0,-1]

#一つ目の方法
class RollingHash():
    def __init__(self, s, base, mod):
        self.mod = mod
        self.pw = pw = [1]*(len(s)+1)
 
        l = len(s)
        self.h = h = [0]*(l+1)
 
        v = 0
        for i in range(l):
            h[i+1] = v = (v * base + ord(s[i])) % mod #文字ではなく数字のリストの場合はord不要
        v = 1
        for i in range(l):
            pw[i+1] = v = v * base % mod
    def get(self, l, r): #S[l:r)indexでいうl文字目からr-1文字目
        return (self.h[r] - self.h[l] * self.pw[r-l]) % self.mod

base1 = 1007; base2 = 2009
mod1 = 1000000007; mod2 = 1000000009

def main():
    N = int(input())
    A = list(map(int,input().split()))
    S = list(str(input()))
    AS = []
    for i in range(N-1):
        if A[i] < A[i+1]:
            AS.append('<')
        else:
            AS.append('>')
    #print(AS,S)
    #操作不要
    if AS == S:
        print(0);exit()
    #ループする場合
    if A[N-1] < A[0]:
        AS.append('<')
    else:
        AS.append('>')

    #print(AS)
    RHS1 = RollingHash(S,base1,mod1) #N-1文字
    RHA1 = RollingHash(AS,base1,mod1) #N文字
    RHS2 = RollingHash(S,base1,mod1) #N-1文字
    RHA2 = RollingHash(AS,base1,mod1) #N文字
    #print(RHS.get(0,N-1))
    for i in range(1,N):
        #[i,N) + [0,i-1)
        mid = N - i
        if RHS1.get(0,mid) == RHA1.get(i,N) and RHS1.get(mid,N-1) == RHA1.get(0,i-1):
            if RHS2.get(0,mid) == RHA2.get(i,N) and RHS2.get(mid,N-1) == RHA2.get(0,i-1):
                print(i);exit()
    print(-1)


if __name__ == '__main__':
    main()