N = int(input())
S = input()
L = list(S)
ans = set()

for i in range(N-1):
    a,b = L[i],L[i+1]
    L = list(S)
    L[i], L[i+1] = "B", "B"
    ans.add("".join(L))
    L[i], L[i+1] = a, b
    
print(len(ans))