function ccc13(form) {
    factor = 3;
    sum = 0;
    for (index = form.numero.value.length; index > 0; --index) {
        sum = sum + form.numero.value.substring (index-1, index) * factor;
        factor = 4 - factor;
    }
    cc = ((1000 - sum) % 10);
    form.chiffre.value = "0" + form.numero.value + cc;
    result = form.chiffre.value;
    form.cc.value = cc;
    if (form.numero.value.length!=12){
        alert("UPOZORNĚNÍ ! Prosím zapište 12 čísel");
        form.cc.value = "";
        form.chiffre.value = "";
    }
}

function cccgln(form) {
    factor = 3;
    sum = 0;
    for (index = form.numero.value.length; index > 0; --index) {
        sum = sum + form.numero.value.substring (index-1, index) * factor;
        factor = 4 - factor;
    }
    cc = ((1000 - sum) % 10);
    form.cc.value = cc;
    if (form.numero.value.length!=12){
        alert("UPOZORNĚNÍ ! Prosím zapište 12 čísel");
        form.cc.value = "";
    }
}

function ccc8(form) {
    factor = 3;
    sum = 0;
    for (index = form.numero.value.length; index > 0; --index) {
        sum = sum + form.numero.value.substring (index-1, index) * factor;
        factor = 4 - factor;
    }
    cc = ((1000 - sum) % 10);
    form.chiffre.value = "000000" + form.numero.value + cc;
    result = form.chiffre.value;
    form.cc.value = cc;
    if (form.numero.value.length!=7){
        alert("UPOZORNĚNÍ ! Prosím zapište 7 čísel");
        form.cc.value = "";
        form.chiffre.value = "";
    }
}

function ccc12(form) {
    factor = 3;
    sum = 0;
    for (index = form.numero.value.length; index > 0; --index) {
        sum = sum + form.numero.value.substring (index-1, index) * factor;
        factor = 4 - factor;
    }
    cc = ((1000 - sum) % 10);
    form.chiffre.value = "00" + form.numero.value + cc;
    result = form.chiffre.value;
    form.cc.value = cc;
    if (form.numero.value.length!=11){
        alert("UPOZORNĚNÍ ! Prosím zapište 11 čísel");
        form.cc.value = "";
        form.chiffre.value = "";
    }
}

function ccc14(form) {
    factor = 3;
    sum = 0;
    for (index = form.numero.value.length; index > 0; --index) {
        sum = sum + form.numero.value.substring (index-1, index) * factor;
        factor = 4 - factor;
    }
    cc = ((1000 - sum) % 10);
    form.chiffre.value = form.numero.value + cc;
    result = form.chiffre.value;
    form.cc.value = cc;
    if (form.numero.value.length!=13){
        alert("UPOZORNĚNÍ ! Prosím zapište 13 čísel");
        form.cc.value = "";
        form.chiffre.value = "";
    }
}

function ccc18(form) {
    factor = 3;
    sum = 0;
    for (index = form.numero.value.length; index > 0; --index) {
        sum = sum + form.numero.value.substring (index-1, index) * factor;
        factor = 4 - factor;
    }
    cc = ((1000 - sum) % 10);
    form.cc.value = cc
    if (form.numero.value.length!=17){
        alert("UPOZORNĚNÍ ! Prosím zapište 17 čísel");
        form.cc.value = "";
    }
}