diff --git a/tuto-pysdur/pgcd.py b/tuto-pysdur/pgcd.py
index 6618b0c..00137bc 100755
--- a/tuto-pysdur/pgcd.py
+++ b/tuto-pysdur/pgcd.py
@@ -13,6 +13,9 @@ The goal is to build durable python script using standard library
 This script compute the greater common divisor of 2 integrers
 """
 
+# MESSAGES
+WRONG_INPUT_ORDER = "Inputs in ascending order"
+
 
 def pgcd(input_a, input_b):
     """
@@ -50,6 +53,7 @@ if __name__ == "__main__":
 
     # ARGUMENTS, PARAMETERS & OPTIONS
     import argparse
+    import logging
     import sys
 
     PARSER = argparse.ArgumentParser(
@@ -61,12 +65,21 @@ if __name__ == "__main__":
     PARSER.add_argument(
         "-v", "--verbose", help="A near mathematics answer", action="store_true"
     )
+
     ARGS = PARSER.parse_args()
 
-    # DO THE JOB
-    NEW_PGCD = pgcd(ARGS.INPUT_A, ARGS.INPUT_B)
+    # CHECKS INPUTS
+    if ARGS.INPUT_A <= ARGS.INPUT_B:
+        logging.critical(WRONG_INPUT_ORDER)
+        sys.exit()
 
+    # DO THE JOB
+    else:
+        NEW_PGCD = pgcd(ARGS.INPUT_A, ARGS.INPUT_B)
+
+    # RESPONSE
     if ARGS.verbose:
         print(f"PGCD({ARGS.INPUT_A};{ARGS.INPUT_B}) = {NEW_PGCD}")
+
     else:
         print(NEW_PGCD)