.py program that finds the greatest of 5 numbers

Only executes if input is 5 numbers no more, no less

greatest number.py

@@ -0,0 +1,16 @@
+def greatest_number():
+    a=list(map(int,input("Input the 5 numbers with spaces - ").split(' ')))
+    if len(a)==5:
+        flag=a[0]
+        for i in a[1:]:
+            if i>=flag:
+                flag=i
+            else:
+                continue
+        print("The greatest number is",flag)
+    else:
+        print('You were supposed to enter 5 numbers.')
+
+
+greatest_number()
+