MOD = 10**9 + 7

n = int(input())
s = input().strip()

ans = 0
expected = 'A'

for i in range(n, 0, -1):
    current = s[i-1]
    if current == expected:
        continue
    # Find the other peg which is not current or expected
    if expected != 'A' and current != 'A':
        other = 'A'
    elif expected != 'B' and current != 'B':
        other = 'B'
    else:
        other = 'C'
    ans += pow(2, i-1, MOD)
    ans %= MOD
    expected = other

print(ans % MOD)