import sys

sys.setrecursionlimit(200005)
# sys.set_int_max_str_digits(200005)
int1 = lambda x: int(x)-1
pDB = lambda *x: print(*x, end="\n", file=sys.stderr)
p2D = lambda x: print(*x, sep="\n", end="\n\n", file=sys.stderr)
def II(): return int(sys.stdin.readline())
def LI(): return list(map(int, sys.stdin.readline().split()))
def LLI(rows_number): return [LI() for _ in range(rows_number)]
def LI1(): return list(map(int1, sys.stdin.readline().split()))
def LLI1(rows_number): return [LI1() for _ in range(rows_number)]
def SI(): return sys.stdin.readline().rstrip()

dij = [(0, 1), (-1, 0), (0, -1), (1, 0)]
# dij = [(0, 1), (-1, 0), (0, -1), (1, 0), (1, 1), (1, -1), (-1, 1), (-1, -1)]
# inf = -1-(-1 << 31)
inf = -1-(-1 << 62)

# md = 10**9+7
md = 998244353

# from random import randrange
#
# BASE = randrange(128, 256)
# MOD = 2147483629
#
# class RollingHash:
#     def __init__(self, target):
#         self.N = len(target)
#         self.table = [0]
#         self.power = [1]
#         for c in target:
#             self.table += [(self.table[-1]*BASE)%MOD+c]
#             self.power += [self.power[-1]*BASE%MOD]
#
#     def hashing(self, s):
#         h = 0
#         for c in s:
#             h = h*BASE%MOD+c
#         return h%MOD
#
#     def hash_lr(self, l, r):
#         return (self.table[r]-self.table[l]*self.power[r-l]%MOD)%MOD
#
#     def find(self, s, start=0):
#         h = self.hashing(s)
#         for i in range(start, self.N-len(s)+1):
#             if self.hash_lr(i, i+len(s)) == h:
#                 return i
#         return -1
#
#     def find_all(self, s):
#         res = []
#         h = self.hashing(s)
#         for i in range(self.N-len(s)+1):
#             if self.hash_lr(i, i+len(s)) == h:
#                 res.append(i)
#         return res
#
# def todd(s):
#     # print(s)
#     dd=[]
#     r=n-1
#     while not s[r]:r-=1
#     p=r
#     for i in range(r+1):
#         if s[i]:
#             dd.append((i-p)%n)
#             p=i
#     return dd

n=II()
aa=LI()
s=[c==">" for c in  SI()]
s1=sum(s)
t=[aa[i]>aa[i+1] for i in range(n-1)]
t.append(aa[n-1]>aa[0])
t1=sum(t)
if s1==t1:
    s.append(False)
elif s1+1==t1:
    s.append(True)
else:
    print(-1)
    exit()

def tox(s):
    x=0
    for i,c in enumerate(s):
        if c:x|=1<<i
    return x

x=tox(s)
y=tox(t)
for i in range(n):
    if x==y:
        print(i)
        exit()
    d=y&1
    y|=d<<n
    y>>=1

# sd=todd(s)
# td=todd(t)
# print(s)
# print(t)
# print(sd)
# print(td)
#
# rh=RollingHash(td+td)
# hs=rh.hashing(s)
# for i in range(n):
#     if rh.hash_lr(i,i+n)==hs:
#         print(i)
#         exit()
print(-1)