'using namespace std' is causing a strange behaviour [duplicate]

This question already has an answer here:

• Why should I not #include <bits/stdc++.h>? 3 answers

I ran the following 2 snippets of code, which are the same except the usage of "namespace std" in the second. I am not able to understand the reason why their outputs are different. Can someone please guide me? Thanks!

http://ift.tt/2lN4mhJwithout namespace

http://ift.tt/2lMTFvDwith namespace std