Simple Calculator using functions

def su(a,b):  
      c=a+b
      print 'Added value is:',c
     
def subt(a,b):
            if a>b:
                  c=a-b
                  print 'Subtracted value is:',c
            else:
                  c=b-a
                  print 'Subtracted value is:',c
                  
def mul(a,b):
      c=a*b
      print 'Multiplication value is:',c

def div(a,b):
      if b==0:         
            print 'Division by zero not defined'
      else:
            c=float(a)/b
            print 'Divison value is:',c

def exp(a,b):
      c=a**b
      print 'Exponent value is:',c


a=int(raw_input('Enter the value of a:'))
b=int(raw_input('Enter the value of b:'))
print ' 1. add  2.sub  3.mul  4. div  5.exp'
n=int(raw_input('Enter the choice:'))
if n==1:
      su(a,b)        # Function call
elif n==2:
      subt(a,b)    # Function call
elif n==3:
      mul(a,b)          # Function call
elif n==4:
      div(a,b)    # Function call
elif n==5:
      exp(a,b)    # Function call
else:
      print 'Invalid options'