function cal_pace(d,h,m,s){
 var distance = d;
 var hours = h;
 var minutes = m;
 var seconds = s;
 if(distance.length > 0 && hours.length > 0 && minutes.length > 0 && seconds.length > 0)
 {
  var speed = parseFloat(hours) * 60.0 + parseFloat(minutes) + parseFloat(seconds) / 60.0;
  speed = speed / parseFloat(distance);
  var speed_minutes = Math.floor(speed);
  var speed_seconds = Math.floor((speed - speed_minutes) * 60.0);
  return (speed_minutes + '\'' + speed_seconds + '\"').toString();
 }
 return '0\'0\"';
}