program
  decl
    type
      int
    name
      a
    ,
    name
      b
    ;
  stmt
    name
      a
    =
    expr
      number
        0
    ;
  stmt
    while
    (
    cond
      expr
        name
          a
      comp
        ==
      expr
        number
          0
    )
    stmt
      {
      stmt
        name
          a
        =
        read
        (
        )
        ;
      }
  stmt
    name
      b
    =
    read
    (
    )
    ;
  stmt
    if
    (
    cond
      expr
        name
          b
      comp
        >
      expr
        name
          a
    )
    stmt
      {
      stmt
        while
        (
        cond
          expr
            name
              b
          comp
            >
          expr
            name
              a
        )
        stmt
          {
          stmt
            write
            (
            expr
              name
                b
            )
            ;
          stmt
            name
              b
            =
            expr
              expr
                name
                  b
              binop
                -
              expr
                name
                  a
            ;
          }
      stmt
        write
        (
        expr
          name
            a
        )
        ;
      }