// 最左侧冗余覆盖子串
    func HW2023028() {
        // 测试用例
//        let s1 = "ab", s2 = "aabcd", k = 1
//        let s1 = "abc", s2 = "dfs", k = 2
        // 开始代码
        let s1 = String(readLine()!)
        let s2 = String(readLine()!)
        let k = Int(readLine()!)!
        let strLen = s1.count + k
        let len = s2.count - strLen + 1
        var res = -1
        for i in 0..<(len>0 ? len : 0) { // 滑动窗口
            let temp = String(s2.dropFirst(i).prefix(strLen))
            // 判断s1是否是temp的子串，如果是则返回当前下标
            if Set(Array(s1)).isSubset(of: Set(Array(temp))) {
                res = i
                break
            }
        }
        print(res)
    }