On a bridge are $n$ stations, equally spaced. Meaning $A_0$ is the left exit of the bridge, $A_1$ is $1$ distance unit (let's say meters) away from that, $A_2$ is $1$ meter away from that and so on, until $A_{99}$ which is the right exit of the bridge.
You are at $A_i$. You are quite an eccentric fellow, and each time you walk somewhere, you have $p$ probability to walk left and $1-p$ probability to walk right.
What is the probability you will exit the bridge from $A_0$? What is the probability you will exit from $A_{99}$?