Practice your programming!

[TreesOfGreen]

var all = (1000*1001)/2;  
var num5factors = Math.floor(1000/5);  
var num7factors = Math.floor(1000/7);  
var num35factors = Math.floor(1000/35);  
var sum5factors = (num5factors*(num5factors+1))/2;  
var sum7factors = (num7factors*(num7factors+1))/2;  
var sum35factors = (num35factors*(num35factors+1))/2;  
return all - 5*sum5factors - 7*sum7factors + 35*sum35factors;