Question

how to input my program to see the result

Answer 1

You can get input for the console most of the time. Of course, you could get user input from other sources as well, such as the mouse, the microphone, various game controllers, and whatnot. Online GDB runs on a remote server, so we're limited to console (standard input).

You have various functions in various languages. For instance, in Python, you'd use input(). In C, you'd use scanf().

What's your language?

Answer 2

Simply use your language's built-in input function in your code, then when you click Run, type your input directly into the console at the bottom of the screen and press Enter.

Answer 3

Simply type your input code (for Python, use input(), for Java, import java.util.Scanner; then define Scanner variable_name_here = new Scanner). No matter the language, there will be a cursor blinking, indicating a place to type. Click there, type your input and watch your code run!