MOD = 10 ** 9 + 7

n = int(input())
C = [0]
for _ in range(n):
    C.append(C[-1] * 2 + 1)

S = input().rstrip("A")
if not S:
    print(0)
    exit()

if len(S) == 1:
    print(1)
    exit()

b = 0
ans = 0

for i in range(len(S) - 1, -1, -1):
    s = "ABC".index(S[i])
    if s != b:
        ans += C[i] + 1
        ans %= MOD
        b = 3 ^ b ^ s

print(ans)