diff --git a/unit05_key_exchange/src/c_03.py b/unit05_key_exchange/src/c_03.py
index d750024..f9bb88b 100644
--- a/unit05_key_exchange/src/c_03.py
+++ b/unit05_key_exchange/src/c_03.py
@@ -1,10 +1,9 @@
 import random
-import base64
 import hashlib
 import sys
 
 g=9
-p=1001
+p=997
 
 a=random.randint(5, 10)
 
@@ -13,22 +12,22 @@ b=random.randint(10,20)
 A = (g**a) % p
 B = (g**b) % p
 
-print 'g: ',g,' (a shared value), n: ',p, ' (a prime number)'
+print ('g: ',g,' (a shared value), n: ',p, ' (a prime number)')
 
-print '\nAlice calculates:'
-print 'a (Alice random): ',a
-print 'Alice value (A): ',A,' (g^a) mod p'
+print ('\nAlice calculates:')
+print ('a (Alice random): ',a)
+print ('Alice value (A): ',A,' (g^a) mod p')
 
-print '\nBob calculates:'
-print 'b (Bob random): ',b
-print 'Bob value (B): ',B,' (g^b) mod p'
+print ('\nBob calculates:')
+print ('b (Bob random): ',b)
+print ('Bob value (B): ',B,' (g^b) mod p')
 
-print '\nAlice calculates:'
+print ('\nAlice calculates:')
 keyA=(B**a) % p
-print 'Key: ',keyA,' (B^a) mod p'
-print 'Key: ',hashlib.sha256(str(keyA)).hexdigest()
+print ('Key: ',keyA,' (B^a) mod p')
+print ('Key: ',hashlib.sha256(str(keyA).encode()).hexdigest())
 
-print '\nBob calculates:'
+print ('\nBob calculates:')
 keyB=(A**b) % p
-print 'Key: ',keyB,' (A^b) mod p'
-print 'Key: ',hashlib.sha256(str(keyB)).hexdigest()
\ No newline at end of file
+print ('Key: ',keyB,' (A^b) mod p')
+print ('Key: ',hashlib.sha256(str(keyB).encode()).hexdigest()