function changecity(){
index = Form1.sf.options.selectedIndex-1;
Form1.city.length = city[index].length;
for(var i = 0;i<city[index].length;i++)
{
var text = city[index][i].split("-");
Form1.city.options[i].text = text[0];
Form1.city.options[i].value =text[1];
}
}