n = io.read("*n", "*l")
s = io.read()
cnt = 0
for i = 1, n-2 do
    u = string.sub(s, i, i)
    if(u == "U") then
        diffmax = (n - i) / 2
        for d = 1, diffmax do
            if(string.sub(s, i + d, i + d) == "M" and string.sub(s, i + 2 * d, i + 2 * d) == "G") then
                cnt = cnt + 1
            end
        end
    end
end
print(cnt)