Split array in group of n element.

Question

I have one array called ans[i]. 

ans[i]={1 2 3 4 5 6 7 8 9 10 11 12 13 14 } //n no.of inputed element.

and i want to split in group of 3 and sum of 3-3 elements and stored it in array.Like this

 

res[0]=6

res[1]=15

res[2]=24....like  this.