import sys import pypyjit import itertools import heapq import math from collections import deque, defaultdict import bisect input = sys.stdin.readline sys.setrecursionlimit(10 ** 6) pypyjit.set_param('max_unroll_recursion=-1') def index_lt(a, x): 'return largest index s.t. A[i] < x or -1 if it does not exist' return bisect.bisect_left(a, x) - 1 def index_le(a, x): 'return largest index s.t. A[i] <= x or -1 if it does not exist' return bisect.bisect_right(a, x) - 1 def index_gt(a, x): 'return smallest index s.t. A[i] > x or len(a) if it does not exist' return bisect.bisect_right(a, x) def index_ge(a, x): 'return smallest index s.t. A[i] >= x or len(a) if it does not exist' return bisect.bisect_left(a, x) N = int(input()) S = input()[:-1] cands = set() for i, (s, t) in enumerate(zip(S[:-1], S[1:])): acc = () if s == 'A': acc += (i,) if t == 'A': acc += (i + 1,) cands.add(acc) print(len(cands))