fun readLargeInt () =
    valOf (TextIO.scanStream (LargeInt.scan StringCvt.DEC) TextIO.stdIn)


val () =
    let
        val x = readLargeInt ()
        val y = readLargeInt ()
        val z = readLargeInt ()

        val x_included = if x <= z then 1 else 0
        val y_included = if y <= z then 1 else 0
        val ans = z - (x_included + y_included)
    in
        print (LargeInt.toString ans ^ "\n")
    end