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
        v = 1
        for i in range(l):
            pw[i+1] = v = v * base % mod
    def get(self, l, r):
        return (self.h[r] - self.h[l] * self.pw[r-l]) % self.mod

base = 37; mod = 10**9 + 9

N = int(input())
A = list(map(int, input().split())) 
A = A+[A[0]]
S = input()
L = []
for i in range(N):
    if A[i]<A[i+1]:
        L.append('<')
    else:
        L.append('>')
L = ''.join(map(str, L))*2
SRH = RollingHash(S,base,mod)
LRH = RollingHash(L,base,mod)
m = SRH.get(0,len(S))
for i in range(N):
    if m == LRH.get(i,len(S)+i):
        print(i)
        exit()
print(-1)