def summi(num):
    if num == 1:
        return 1
    if num == 0:
        return 0
    if num == 2:
        return 3
    return num + summi(num-1)



def substrCount(n, s):
    stri = []
    count = 0
    for i,a in groupby(s):
        stri.append((i , len(list(a))))
    for i in range(len(stri)):
        count += summi(stri[i][1])
    for i in range(len(stri)-2):
        if stri[i][0] == stri[i+2][0] and stri[i+1][1] == 1:
            count += min(stri[i][1] , stri[i+2][1])
    return count