diff --git a/lecture note4-operation.py b/lecture note4-operation.py
new file mode 100644
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--- /dev/null
+++ b/lecture note4-operation.py	
@@ -0,0 +1,66 @@
+Python 3.7.1 (v3.7.1:260ec2c36a, Oct 20 2018, 03:13:28) 
+[Clang 6.0 (clang-600.0.57)] on darwin
+Type "help", "copyright", "credits" or "license()" for more information.
+>>> 
+============= RESTART: /Users/kimminsub/Documents/HELLO_WORLD.py =============
+HELLO, WORLD.
+>>> #이것은 주석입니다.
+>>> a=2020
+>>> a
+2020
+>>> b= a+3030
+>>> b
+5050
+>>> a=3
+>>> b=123456789
+>>> c=123456789012345678901234567890
+>>> a
+3
+b
+>>> 
+>>> c
+123456789012345678901234567890
+d
+>>> a
+3
+>>> b
+123456789
+>>> c
+123456789012345678901234567890
+>>> d
+Traceback (most recent call last):
+  File "<pyshell#14>", line 1, in <module>
+    d
+NameError: name 'd' is not defined
+>>> d= -12345678901234567890123456789012345677890
+>>> d
+-12345678901234567890123456789012345677890
+>>> e=-123456789
+>>> e
+-123456789
+>>> f=-3
+>>> 
+>>> f
+-3
+>>> type(f)
+<class 'int'>
+>>> type(d)
+<class 'int'>
+>>> type(e)
+<class 'int'>
+>>> a= 3+4
+>>> a
+7
+>>> b=7-10
+>>> b
+-3
+>>> c=7*-3
+>>> c
+-21
+>>> d=30//7
+>>> d
+4
+>>> e= 30%7
+>>> e
+2
+>>>