fun readInt () =
    valOf (TextIO.scanStream (Int.scan StringCvt.DEC) TextIO.stdIn)


val () =
    let
        val l = readInt ()
        val r = readInt ()
        val m = readInt ()
        
        val ans = Int.min(m, r - l + 1)
    in
        print (Int.toString ans ^ "\n")
    end