import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines

import numpy as np

N = int(readline())
S = np.frombuffer(read(),'S1')[:N]

M = (S == b'M')
U = (S == b'U')
G = (S == b'G')

answer = 0
for i in np.where(M)[0]:
    L = min(i, N-1-i)
    left = U[:i][::-1][:L]
    right = G[i+1:][:L]
    answer += np.count_nonzero(left&right)

print(answer)