n = int(input())
s = input()

ans = 0

for i in range(n):
    if s[i] == "U":
        for j in range(1,n//2+1):
            if i+j*2 >= n:
                break
            if s[i+j] == "M" and s[i+j*2] == "G":
                ans += 1

print(ans)