diff --git a/src/main/java/ac/cnu/realcoding/controller/UrlShortenerController.java b/src/main/java/ac/cnu/realcoding/controller/UrlShortenerController.java
index 35ecf3b..02379fe 100644
--- a/src/main/java/ac/cnu/realcoding/controller/UrlShortenerController.java
+++ b/src/main/java/ac/cnu/realcoding/controller/UrlShortenerController.java
@@ -24,10 +24,27 @@ public UrlShortenerController(UrlShortenerService urlShortenerService) {
         this.urlShortenerService = urlShortenerService;
     }
 
-    @GetMapping("health")
-    public Mono<String> healthCheck() {
+    @GetMapping("health/{n}") //{} 변수로 처리하겠다.
+    public Mono<String> healthCheck(@PathVariable int n) {
         // For basic tutorial
-        return Mono.just("Hello World");
+        return fib(n).map(element -> {
+            return String.valueOf(element);
+        });
+    }
+
+    private Mono<Integer> fib(int n) {
+        if(n==0) {
+            return Mono.just(0);
+        }
+        if(n==1 || n==2) {
+            return Mono.just(1);
+        }
+
+        Mono<Integer> f0 = fib(n-1);
+        Mono<Integer> f1 = fib(n-2);
+        return Mono.zip(f0, f1, (n0, n1) -> {
+            return n0+n1;
+        });
     }
 
     @GetMapping("{encoded}")
diff --git a/src/main/java/ac/cnu/realcoding/encoding/Base62Processor.java b/src/main/java/ac/cnu/realcoding/encoding/Base62Processor.java
index e35c1ad..1d42de7 100644
--- a/src/main/java/ac/cnu/realcoding/encoding/Base62Processor.java
+++ b/src/main/java/ac/cnu/realcoding/encoding/Base62Processor.java
@@ -6,11 +6,22 @@ public class Base62Processor {
 
     public static String encode(long number) {
         // TODO: Implement Base62 Encoding Algorithm.
-        return "";
+
+        StringBuilder sb = new StringBuilder();
+        do {
+            sb.append(CODEC.charAt((int)(number%BASE)));
+            number /= BASE;
+        } while (number > 0);
+        return sb.reverse().toString();
     }
 
     public static long decode(String encoded) {
         // TODO: Implement Base62 Decoding Algorithm.
-        return 0;
+        long sum = 0;
+        for(Character ch : encoded.toCharArray()) {
+            sum *= BASE;
+            sum += CODEC.indexOf(ch);
+        }
+        return sum;
     }
 }
diff --git a/src/main/java/ac/cnu/realcoding/repository/URLInformation.java b/src/main/java/ac/cnu/realcoding/repository/URLInformation.java
index 6003786..d9f3490 100644
--- a/src/main/java/ac/cnu/realcoding/repository/URLInformation.java
+++ b/src/main/java/ac/cnu/realcoding/repository/URLInformation.java
@@ -9,6 +9,9 @@ public class URLInformation {
     @Id
     private Long id;
 
+    private String url;
+
     public URLInformation(String url) {
+        this.url=url;
     }
 }
diff --git a/src/main/java/ac/cnu/realcoding/service/UrlShortenerService.java b/src/main/java/ac/cnu/realcoding/service/UrlShortenerService.java
index 8bb4c5c..70b970a 100644
--- a/src/main/java/ac/cnu/realcoding/service/UrlShortenerService.java
+++ b/src/main/java/ac/cnu/realcoding/service/UrlShortenerService.java
@@ -2,6 +2,8 @@
 
 import java.net.URI;
 
+import ac.cnu.realcoding.encoding.Base62Processor;
+import ac.cnu.realcoding.repository.URLInformation;
 import org.springframework.stereotype.Service;
 
 import ac.cnu.realcoding.configurations.ApplicationConfiguration;
@@ -9,6 +11,7 @@
 import ac.cnu.realcoding.models.UrlShortenerResponse;
 import ac.cnu.realcoding.repository.URLRepository;
 import lombok.RequiredArgsConstructor;
+import org.springframework.web.util.UriComponentsBuilder;
 import reactor.core.publisher.Mono;
 
 @Service
@@ -22,7 +25,10 @@ public Mono<URI> unshortenUrl(String encoded) {
         // Problem A: Decode encoded String
         // Problem B: Get full url by querying decoded PK.
         // Problem C: if encoded string is invalid or not found return Bad Request
-        return Mono.error(new UnsupportedOperationException("not implemented"));
+        return Mono.just(Base62Processor.decode(encoded))
+                .flatMap(decoded -> urlRepository.findById(decoded))
+                .map(URLInformation::getUrl)
+                .map(URI::create);
     }
 
     public Mono<UrlShortenerResponse> shortenUrl(UrlShortenerRequest urlShortenerRequest) {
@@ -30,6 +36,16 @@ public Mono<UrlShortenerResponse> shortenUrl(UrlShortenerRequest urlShortenerReq
         // Problem B: Insert to database and get PK from database, PK should be auto-generated integer.
         // Problem C: Encode PK by using Base 63.
         // Problem D: Build UrlShortenerResponse with server host and port.
-        return Mono.error(new UnsupportedOperationException("not implemented"));
+        String url = urlShortenerRequest.getUrl();
+        return urlRepository.save(new URLInformation(url))
+                .map(URLInformation::getId)
+                .map(Base62Processor::encode)
+                .map(encoded -> UriComponentsBuilder.newInstance()
+                        .scheme("http")
+                        .host(applicationConfig.getHost())
+                        .port(applicationConfig.getPort())
+                        .path(encoded)
+                        .toUriString())
+                .map(UrlShortenerResponse::of);
     }
 }