// Phase 200-B: Minimal atoi with digits capture
static box Main {
    main() {
        local s = "123"
        local digits = "0123456789"  // ← Captured var

        local i = 0
        local v = 0
        local n = s.length()

        loop(i < n) {
            local ch = s.substring(i, i+1)
            local pos = digits.indexOf(ch)  // ← Uses captured digits

            if pos < 0 {
                break
            }

            v = v * 10 + pos
            i = i + 1
        }

        print(v)  // Expected: 123
    }
}