function Calc()
{
  var loan = document.getElementById("loan").value;
  var interest = document.getElementById("interest").value;
  var month = document.getElementById("month").value;
  if(loan.length==0 || interest.length==0 || month.length==0)
  {
    document.getElementById("month_sum").value="נתונים חסרים";
    return;
  } 
  var ld = parseFloat(loan);
  var id = parseFloat(interest);
  var md = parseFloat(month);
  if(ld <= 1000.0 || id <= 1.0 || md <= 3.0)
  {
    document.getElementById("month_sum").value="נתונים שגויים";
    return;
   }
    
  var i = id/1200.0;
  var r = Math.pow(1.0+i,md);
  r = 1.0 - 1/r;
  var mp = ld*i/r;
  mp=Math.round(mp);
  var tp = mp*md;
  tp=Math.round(tp);
  document.getElementById("month_sum").value=mp.toString();
  document.getElementById("total_sum").value=tp.toString();
}