// Minimal self-contained eval (no using): collect the first Print(Literal int) and print it
static box Main {
  // helper: find from position
  index_of_from(hay, needle, pos) {
    if pos < 0 { pos = 0 }
    if pos >= hay.length() { return -1 }
    local tail = hay.substring(pos, hay.length())
    local rel = tail.indexOf(needle)
    if rel < 0 { return -1 } else { return pos + rel }
  }
  main(args) {
    local json = "{\"kind\":\"Program\",\"statements\":[{\"kind\":\"Print\",\"expression\":{\"kind\":\"Literal\",\"value\":{\"type\":\"int\",\"value\":42}}}]}"
    // naive collect: first Print of Literal int
    local ki = "\"expression\":{\"kind\":\"Literal\",\"value\":{\"type\":\"int\",\"value\":"
    local p = json.indexOf(ki)
    if p >= 0 {
      local i = p + ki.length()
      local j = i
      loop (true) {
        local ch = json.substring(j, j+1)
        if ch == "" { break }
        if ch == "0" || ch == "1" || ch == "2" || ch == "3" || ch == "4" || ch == "5" || ch == "6" || ch == "7" || ch == "8" || ch == "9" { j = j + 1  continue }
        break
      }
      local digits = json.substring(i, j)
      if digits { print(digits) }
    }
    return 0
  }
}