var str;var val1;var val2;var val3;

function setValToNull (){val1=0;val2=0;val3=0; return true}

function sum () {return val1+val2+val3;}

function check() {
if (sum()==0) {alert('Die Frage ist nicht beantwortet !');return false};
return true}

var OK=false;

function doOpen() {
window.location="solution.html";
return 1;
}