Check The Type Of Triangle

#This program checks whether a triangle is isoceless or equilateral or scalian
def triangletype(s1,s2,s3):
    if s1=='' or s2=='' or s3=='':
        print "I think you had forgotten to enter one side"
    else:
        if s1==s2 and s2==s3:
            print "Triangle is equilateral"
        elif s1==s2 or s2==s3 or s3==s1:
            print "Trianlge is isocless"
        else:
            print "It is scalian"

s1=raw_input("Enter the length of side 1:")
s2=raw_input("Enter the length of side 2:")
s3=raw_input("Enter the length of side 3:")
triangletype(s1,s2,s3)
raw_input("")