diff --git a/day4/day4.py b/day4/day4.py
new file mode 100644
index 0000000..360be68
--- /dev/null
+++ b/day4/day4.py
@@ -0,0 +1,37 @@
+#! /usr/bin/env python3
+
+
+def check_increase(number):
+    num = str(number)
+    for i in range(len(num) - 1):
+        if num[i+1] < num[i]:
+            return False
+    return True
+
+def check_adjacent(number):
+    num = str(number)
+    for digit in num:
+        count = num.count(digit)
+        if count == 2: # Part one : <= 2
+            return True
+    return False
+
+
+def tests():
+    assert check_increase(123456) == True
+    assert check_increase(123454) == False
+    assert check_adjacent(112345) == True
+    assert check_adjacent(123445) == True
+    assert check_adjacent(123456) == False
+
+
+def main(start, end):
+    matches = 0
+    for n in range(start, end + 1):
+        if check_increase(n) and check_adjacent(n):
+            matches += 1
+    return matches
+
+if __name__ == "__main__":
+    tests()
+    print("Matches : ", main(367479, 893698))