import math
import sys

n = int(input())
s = input()
idx_1 = 0
ans = 0
for i in s:
    idx_1 += 1
    if i == 'U':
        idx_2 = idx_1
        for j in s[idx_1:]:
            idx_2 += 1
            if j == 'M' and idx_2+(idx_2-idx_1)-1 <= n and s[idx_2+(idx_2-idx_1)-1]=='G':
                ans += 1

print(ans)