Two friends are on the coordinate axis Ox in points with integer coordinates. One of them is in the point x1 = a, another one is in the point x2 = b. 

Each of the friends can move by one along the line in any direction unlimited number of times. When a friend moves, the tiredness of a friend changes according to the following rules: the first move increases the tiredness by 1, the second move increases the tiredness by 2, the third — by 3 and so on. For example, if a friend moves first to the left, then to the right (returning to the same point), and then again to the left his tiredness becomes equal to 1 + 2 + 3 = 6.

The friends want to meet in a integer point. Determine the minimum total tiredness they should gain, if they meet in the same point.

Input

The first line contains a single integer a (1 ≤ a ≤ 1000) — the initial position of the first friend. 

The second line contains a single integer b (1 ≤ b ≤ 1000) — the initial position of the second friend.

It is guaranteed that a ≠ b.

Output

Print the minimum possible total tiredness if the friends meet in the same point.

Examples

Input

3
4


Output

1


Input

101
99


Output

2


Input

5
10


Output

9

Note

In the first example the first friend should move by one to the right (then the meeting happens at point 4), or the second friend should move by one to the left (then the meeting happens at point 3). In both cases, the total tiredness becomes 1.

In the second example the first friend should move by one to the left, and the second friend should move by one to the right. Then they meet in the point 100, and the total tiredness becomes 1 + 1 = 2.

In the third example one of the optimal ways is the following. The first friend should move three times to the right, and the second friend — two times to the left. Thus the friends meet in the point 8, and the total tiredness becomes 1 + 2 + 3 + 1 + 2 = 9.
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.Collection;
import java.util.List;
import java.util.Scanner;
import java.util.function.Function;
import java.util.stream.Collectors;
public class _p000931A {
    static public void main(final String[] args) throws IOException {
        p000931A._main(args);
    }
//begin p000931A.java
static private class p000931A extends Solver{public p000931A(){nameIn="p000931A.in"
;singleTest=true;}int a;int b;@Override protected void solve(){int l=Math.abs(a-
b);pw.println(((l/2)*(l/2+1)+(l-l/2)*(l-l/2+1))/2);}@Override public void readInput
()throws IOException{a=sc.nextInt();if(sc.hasNextLine()){sc.nextLine();}b=sc.nextInt
();if(sc.hasNextLine()){sc.nextLine();}}static public void _main(String[]args)throws
IOException{new p000931A().run();}}
//end p000931A.java
//begin net/leksi/contest/Solver.java
static private abstract class Solver{protected String nameIn=null;protected String
nameOut=null;protected boolean singleTest=false;protected boolean preprocessDebug
=false;protected boolean doNotPreprocess=false;protected Scanner sc=null;protected
PrintWriter pw=null;private void process()throws IOException{if(!singleTest){int
t=lineToIntArray()[0];while(t-->0){readInput();solve();}}else{readInput();solve(
);}}abstract protected void readInput()throws IOException;abstract protected void
solve()throws IOException;protected int[]lineToIntArray()throws IOException{return
Arrays.stream(sc.nextLine().trim().split("\\s+")).mapToInt(Integer::valueOf).toArray
();}protected long[]lineToLongArray()throws IOException{return Arrays.stream(sc.nextLine
().trim().split("\\s+")).mapToLong(Long::valueOf).toArray();}protected String joinToString
(final int[]a){return Arrays.stream(a).mapToObj(Integer::toString).collect(Collectors
.joining(" "));}protected String joinToString(final long[]a){return Arrays.stream
(a).mapToObj(Long::toString).collect(Collectors.joining(" "));}@Deprecated protected
String intArrayToString(final int[]a){return joinToString(a);}@Deprecated protected
String longArrayToString(final long[]a){return joinToString(a);}protected<T>String
joinToString(final T[]a){return Arrays.stream(a).map(v->v.toString()).collect(Collectors
.joining(" "));}protected<T>String joinToString(final T[]a,final Function<T,String>
toString){return Arrays.stream(a).map(v->v.toString()).collect(Collectors.joining
(" "));}protected<T>String joinToString(final Collection<T>a){return a.stream().map
(v->v.toString()).collect(Collectors.joining(" "));}protected<T>String joinToString
(final Collection<T>a,final Function<T,String>toString){return a.stream().map(v->
toString.apply(v)).collect(Collectors.joining(" "));}@Deprecated protected List<Long>
longArrayToList(final long[]a){return Arrays.stream(a).mapToObj(Long::valueOf).collect
(Collectors.toList());}@Deprecated protected List<Integer>intArrayToList(final int
[]a){return Arrays.stream(a).mapToObj(Integer::valueOf).collect(Collectors.toList
());}protected List<Long>intArrayToLongList(final int[]a){return Arrays.stream(a
).mapToObj(Long::valueOf).collect(Collectors.toList());}protected List<Integer>toList
(final int[]a){return Arrays.stream(a).mapToObj(Integer::valueOf).collect(Collectors
.toList());}protected List<Long>toList(final long[]a){return Arrays.stream(a).mapToObj
(Long::valueOf).collect(Collectors.toList());}protected void run()throws IOException
{boolean done=false;if(nameIn !=null){try{try(FileInputStream fis=new FileInputStream
(nameIn);PrintWriter pw0=select_output();){done=true;sc=new Scanner(fis);pw=pw0;
process();}}catch(IOException ex){}}if(!done){try(PrintWriter pw0=select_output(
);){sc=new Scanner(System.in);pw=pw0;process();}}}private PrintWriter select_output
()throws FileNotFoundException{if(nameOut !=null){return new PrintWriter(nameOut
);}return new PrintWriter(System.out);}}
//end net/leksi/contest/Solver.java
}
