import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; import java.util.Arrays; import java.util.stream.Stream; public class No00000394_Main2 { static BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); public static void main(String[] args) throws IOException { int[] arr = Stream.of(br.readLine().split(" ")).mapToInt(Integer::parseInt).toArray(); Arrays.sort(arr); int score = 0; for(int i = 1; i <= 4; i++) { score += arr[i]; } System.out.println(String.format("%.2f", score / 4.0)); } }