import Foundationlet input = readLine!splitseparator let n = Intinput0!let k = input2!var o String = Nofor _ in 0n if let line = readLine linecontainsk o = Yes break printo哪错了：m

The error is occurring because input[2] is of type String.Subsequence (also known as Substring), which is a non-optional type. You are trying to force unwrap it using the exclamation mark !, but since it is not an optional, it cannot be force unwrapped.

To fix the error, you can remove the exclamation mark ! from let k = input[2]!:

let k = input[2]

This will assign the value of input[2] to k without force unwrapping it.