import stdio
import c64_basic

array text1 = [ "enter first number:" petscii, 13, 0 ]
array text2 = [ "enter second number:" petscii, 13, 0 ]
array text3 = [ "the sum is:" petscii, 13, 0 ]
array texte = [ "that wasn't a number, try again:" petscii, 13, 0 ]

void main() {
    word a
    word b

    putstrz(text1)
    a = readword()
    while readword_err != 0 {
        putstrz(texte)
        a = readword()
    }

    putstrz(text2)
    b = readword()
    while readword_err != 0 {
        putstrz(texte)
        b = readword()
    }

    putstrz(text3)
    a += b
    putword(a)
    putchar(13)
}