428 - Fail

Fail

Time Limit: 1 sec

**The Problem**

Among **X** students, **B** in Bangla, **M** in Math and **Y** have passed in both subjects in any exam. Find how many students failed in both subjects.

Example

If X = 100, B = 88, M = 80, and Y = 70 then

2 students failed in both subjects.

**The Input**

Input file contain a series of line, each line contain four integer numbers **X, B, M, and Y**(0<**X, B, M, Y**<10000, **X>B, X>M, X>Y, B>Y, M>Y**). Input is terminated by **EOF**.

**The Output**

For each line of input, print how many students failed in both subjects in a separate line.

**Sample Input**

100 88 80 70

100 70 60 50

**Sample Output**

2

20

Problem Setter: Shahin ShamS