diff --git a/README.md b/README.md
index bd90ef0247..6f5139db06 100644
--- a/README.md
+++ b/README.md
@@ -1 +1,4 @@
-# java-calculator-precourse
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+# java-calculator-precourse
+
+1. 커스텀 문자열을 두 개이상의 문자를 받아 커스텀으로 만들기
+2. 덧셈구현 외에도 계산기 시스템 모방하기
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diff --git a/src/main/java/calculator/Application.java b/src/main/java/calculator/Application.java
index 573580fb40..f600cbd54b 100644
--- a/src/main/java/calculator/Application.java
+++ b/src/main/java/calculator/Application.java
@@ -1,7 +1,74 @@
 package calculator;
 
+import camp.nextstep.edu.missionutils.Console;
+import java.util.List;
+import java.util.ArrayList;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
 public class Application {
+
     public static void main(String[] args) {
-        // TODO: 프로그램 구현
+        System.out.println("덧셈할 문자열을 입력해 주세요.");
+        String input = Console.readLine();
+
+        try {
+            int result = add(input);
+            System.out.println("결과 : " + result);
+
+        } catch (IllegalArgumentException e) {
+            throw new IllegalArgumentException(e);
+        }
+    }
+
+    public static String[] splitNumber(String text) {
+        String delimiter = ",|:";
+        String numbersText = text;
+
+        if (text.startsWith("//")) {
+            Matcher matcher = Pattern.compile("//(.)\\\\n(.*)").matcher(text);
+            if (matcher.matches()) {
+                delimiter = Pattern.quote(matcher.group(1));
+                numbersText = matcher.group(2);
+            }
+        }
+
+        return numbersText.split(delimiter);
+    }
+
+    public static int add(String input) {
+        if (input == null || input.isEmpty()) {
+            return 0;
+        }
+
+        String[] numbers = splitNumber(input);
+        return sum(numbers);
+    }
+
+    public static int sum(String[] numbers) {
+        int sum = 0;
+        List<Integer> negativeNumbers = new ArrayList<>();
+
+        for (String numberStr : numbers) {
+            if (numberStr.trim().isEmpty()) {
+                continue;
+            }
+
+            try {
+                int number = Integer.parseInt(numberStr.trim());
+                if (number < 0) {
+                    throw new IllegalArgumentException("잘못");
+                }
+                sum += number;
+            } catch (NumberFormatException e) {
+                throw new IllegalArgumentException();
+            }
+        }
+
+        if (!negativeNumbers.isEmpty()) {
+            throw new IllegalArgumentException();
+        }
+
+        return sum;
     }
-}
+}
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