from collections import defaultdict
import sys


def main():
    input = lambda: sys.stdin.readline()[:-1]
    N = int(input())
    S = input()

    txt = defaultdict(int)
    for i in range(N - 1):
        s = S[:i] + "BB" + S[i + 2 :]
        txt[s] = 1
    ans = sum(txt.values())
    print(ans)


if not __debug__:
    f = open(sys.argv[1], "r")
    sys.stdin = f

main()