diff --git a/lab01-leap-year/test_leap.c b/lab01-leap-year/test_leap.c
index 633579c..b912b5c 100644
--- a/lab01-leap-year/test_leap.c
+++ b/lab01-leap-year/test_leap.c
@@ -6,24 +6,20 @@
 /* return 0 (false) or 1 (true), depending on whether
  * `year` is a leap year or not.
  */
-int is_leap(long year) {
-
-  if (year % 4 != 0) {
-    return 0;
-  }
-
-  if (year % 100 == 0) {
-    return 1;
-  }
-
-  return 0;
+int is_leap(long year)
+{
+  return year % 4 == 0            // Every year that is exactly divisible by four is a leap year
+         && (year % 100 != 0      // except for years that are exactly divisible by 100
+             || year % 400 == 0); // but these centurial years are leap years if they are exactly divisible by 400
 }
 
-int main(int argc, char **argv) {
+int main(int argc, char **argv)
+{
   argc--;
   argv++;
 
-  if (argc != 1) {
+  if (argc != 1)
+  {
     fprintf(stderr, "Error: expected 1 command-line argument (a YEAR), but got %d\n", argc);
     exit(1);
   }
@@ -35,19 +31,25 @@ int main(int argc, char **argv) {
   long year = strtol(argv[0], &end, 10);
   int res_errno = errno;
 
-  if (end == argv[0]) {
+  if (end == argv[0])
+  {
     fprintf(stderr, "Error: couldn't interpret '%s' as a number\n", argv[0]);
     exit(1);
-  } else if (res_errno == ERANGE) {
+  }
+  else if (res_errno == ERANGE)
+  {
     fprintf(stderr, "Error: '%s' is outside the range of numbers we can handle\n", argv[0]);
     exit(1);
-  } else {
-    if (is_leap(year)) {
+  }
+  else
+  {
+    if (is_leap(year))
+    {
       printf("%ld is a leap year\n", year);
-    } else {
+    }
+    else
+    {
       printf("%ld is not a leap year\n", year);
     }
   }
-
 }
-