WA in CONVSTR

can anybody tell me on which test case it is failing.

https://www.codechef.com/viewsolution/33502259

Please help my code passes the sample test case and when both string are same,
And when the one of the variable is already in posn ie. abbabc
abaabc

In this case all cā€™s in the posn. It not convert first string for c.

Please help :pray::pray: