Hi all,
I am a beginner of C++ and I don't know many things. I happens to encounter a simple problem which I don't know how to solve. Please help me out.
I intended to write a program that solve the following problem:

Problem A
Hashmat the brave warrior
Input: standard input
Output: standard output

Hashmat is a brave warrior who with his group of young soldiers moves from one place to another to fight against his opponents. Before fighting he just calculates one thing, the difference between his soldier number and the opponent's soldier number. From this difference he decides whether to fight or not. Hashmat's soldier number is never greater than his opponent.

The input contains two integer numbers in every line. These two numbers in each line denotes the number of soldiers in Hashmat's army and his opponent's army or vice versa. The input numbers are not greater than 2^32. Input is terminated by End of File.

For each line of input, print the difference of number of soldiers between Hashmat's army and his opponent's army. Each output should be in seperate line.

Sample Input:
10 12
10 14
100 200

Sample Output:

This line,
"Input is terminated by End of File."
Because as it said so it will use standard input, I wonder how can we catch this end of file to signify end of program?
I browse some EOF thing of C++, all they involve file operation.
While in this case we do not know the name of the input file,
and the input is from std in.

What can I do?

Thanks all!

Best Wishes,

how can we catch this end of file to signify end of program?

On Windows you can use the Ctrl+Z key combination to signal end-of-file. On POSIX systems you can use Ctrl+D. In code, it's pretty much the same pattern as with files:

int num;

// Read numbers until EOF
while (cin>> num)
    cout<< num <<'\n';
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