from collections import deque
N = int(input())
S = input()

U = deque([])
M = deque([])
G = deque([])

for i,s in enumerate(S):
    if s == "U":
        U.append(i)
    elif s == "M":
        M.append(i)
    else:
        G.append(i)

U,M,G = set(U),set(M),set(G)
ans = 0

flag = True
try:
    minU = min(U)
    maxM = max(M)
    maxG = max(G)
except ValueError:
    flag = False
    print(0)

step = 1
if flag:
    while True:
        if minU+step > maxM or minU+2*step > maxG:
            break
        for n in U:
            if n+step in M and n+2*step in G:
                ans += 1
        step += 1
    print(ans)