How to obtain which checkbutton is selected

checkbutton_2.py

import ctypes
import tkinter


if __name__ == "__main__":
    ctypes.windll.shcore.SetProcessDpiAwareness(1)
    root = tkinter.Tk()

    #variable
    var = tkinter.IntVar(root)

    #display selected checkbutton No.
    label = tkinter.Label(root, textvariable=var)
    label.pack()
    
    #No.1 checkbutton
    check1 = tkinter.Checkbutton(
        root,
        text="check_1",
        variable=var,
        onvalue=1,
        )
    check1.pack()

    #No.2 checkbutton
    check2 = tkinter.Checkbutton(
        root,
        text="check_2",
        variable=var,
        onvalue=2,
        )
    check2.pack()

    #No.3 checkbutton
    check3 = tkinter.Checkbutton(
        root,
        text="check_3",
        variable=var,
        onvalue=3,
        )
    check3.pack()
    root.mainloop()