import sys
input = sys.stdin.readline

def z_algo(s):
    c = 0
    n = len(s)
    z = [0]*n
    
    for i in range(1, n):
        l = i-c
        
        if i+z[l]<c+z[c]:
            z[i] = z[l]
        else:
            j = max(0, c+z[c]-i)
            
            while i+j<n and s[j]==s[i+j]:
                j += 1
            
            z[i] = j
            c = i
    
    z[0] = n
    return z

N = int(input())
A = list(map(int, input().split()))
S = input()[:-1]
l = []

for i in range(N):
    if A[i]<A[(i+1)%N]:
        l.append('<')
    else:
        l.append('>')

s = ''.join(l)
z = z_algo(''.join([S, s, s]))
ans = N+10

for i in range(N-1, 2*N-1):
    if z[i]>=N-1:
        ans = min(ans, i-N+1)

if ans==N+10:
    print(-1)
else:
    print(ans)