TypeError: unsupported operand type(s) for ** or pow(): 'int' and 'str'
<p>Why this code giving error?</p>

<pre><code>def checkfermat(a,b,c,n) :
    if (a**n+b**n)!=c**n :
      print "fermat is absolutely correct.."
    else :
      print "he is wrong"
a=raw_input("enter the first number")
b=raw_input("enter the second num")
c=raw_input("enter the third num")
d=raw_input("enter the fourth num")
checkfermat(a,b,c,d)
</code></pre>

<p>With out the user input section it is showing no errors?                     </p>