// Phase 29ab P6: Pattern6 first-fail minimal (contract violation)
// Expect: JoinIR freeze (step must be i = i + 1)

static box Main {
    find_bad_step(s, ch) {
        local i = 0
        loop(i < s.length()) {
            if s.substring(i, i + 1) == ch {
                return i
            }
            i = i + 2
        }
        return -1
    }

    main() {
        return Main.find_bad_step("abc", "b")
    }
}