N = int(input())
A = list(map(int,input().split()))
S = input()
T = []
for i in range(N-1):
    if A[i] < A[i+1]:
        T.append('<')
    else:
        T.append(">")
if A[-1] < A[0]:
    T.append("<")
else:
    T.append(">")
    
T = "".join(T)
T = S + T + T
n = len(T)
Z = [0] * n
Z[0] = n
i = 1
j = 0
while i < n:
    while i + j < n and T[i+j] == T[j]:
        j += 1
    Z[i] = j
    if j == 0:
        i += 1
        continue
    k = 1
    while k < j and k + Z[k] < j:
        Z[i+k] = Z[k]
        k += 1
    i += k
    j -= k
import sys
for i in range(N-1,n):
    if Z[i] >= N-1:
        print(i-N+1)
        exit()
print(-1)