Describe how a stream cipher works. What is a one-time pad?

A one-time pad is used to send the message $x_{1} x_{2} x_{3} x_{4} x_{5} x_{6} y_{7}$ which is encoded as 0101011. In error, it is reused to send the message $y_{0} x_{1} x_{2} x_{3} x_{4} x_{5} x_{6}$ which is encoded as 0100010 . Show that there are two possibilities for the substring $x_{1} x_{2} x_{3} x_{4} x_{5} x_{6}$, and find them.