Python problem 4

Write a Python program to combine two dictionary adding values for common keys: 

class Solution:
    def add1(self, dic1,dic2):
        for key in dic1.keys():
            if key in dic2.keys():
                dic1[key]=dic1[key]+dic2[key]

        for key in dic2.keys():
            if key not in dic1.keys():
                dic1[key]=dic2[key]


        return(dic1)

kk=Solution()
if __name__=="__main__":
    print(kk.add1({"a":1,"k":3,"u":9},{"a":100,"u":5,"r":100}))