let a, b, s = Scanf.scanf " %d %d %s" @@ fun a b c -> a, b, c
let f s x = let n = ref 0 in String.iter (fun c -> if c = x then incr n) s; !n
let _ = print_endline @@ if s.[a] = '-' && f s '-' = 1 then "Yes" else "No"