var a, bb, x, copy1, y, copy2, z, result, statuscode
body
    read a
    bb := 0
    if a = bb goto GETNUMS
    bb := 1
    if a = bb goto GETNUMS
    goto ERROR

GETNUMS:
    read x
    read y
    bb := 1
    if a <> bb goto SUBNUMS

ADDNUMS:
    copy1 := x
    copy2 := y
    result := x + y
    goto PRINT

SUBNUMS:
    copy1 := y
    copy2 := x
    result := x - y
    goto PRINT

PRINT:
    if a = 0 goto WRITESUBOPS
    write copy1
    write copy2
    goto WRITERESULT

WRITESUBOPS:    
    write copy2
    write copy1
    goto WRITERESULT    

WRITERESULT:    
    z := result
    write z
    statuscode := 0
    goto FINISHED

ERROR:
    statuscode := -1
    goto FINISHED

FINISHED:
    write statuscode
end