Problem in the code answer

#1

when we input the lists as 10 20 30 40 50 60 70 -1 and 5 10 50 60 70 -1 , we get the answer as 10 but i think the answer should be 50;
i have submitted the code and test cases got passed but i still dont understand the answer.
please help me find the logic,

#2

answer will be 10 because the two list you have made are
L1 - 10 20 30 40 50 60 70
L2 - 5 10 20 30 40 50 60 70

your code get accepted because there is not such testcase made
actually this is wrong input because the 2 list should have common values only after intersection point

#3

can you make changes in my code(comp;ete correct code)

#4

you say testcase got passed
so what changes i do

i say input is wrong