let n = stdin.ReadLine().Trim() |> int
let s = stdin.ReadLine().Trim().ToCharArray()

let mutable result = 0

for i in 0 .. n-3 do
    if s.[i] = 'U' then
        for j in i .. n-2 do
            if s.[j] = 'M' && j+j-i < s.Length && s.[j+j-i] = 'G' then
                result <- result + 1

printfn "%d" result