looking help for an effective summation approach

shiyiming

%let x1=2;
%let x2=9;
%let x3=0;
...
%let x50=11;

Suppose Xs above were generated into series of macro variables x1 - x50.
my question, what is the effective way to sum them up?
I tried:

%let sum_x=%sysfunc(&x1.,&x2.,...,&x50.);

but it looks pretty much stupid.
so just wonder anyone can help?

thanks lot and happy new year!

shiyiming

%let x1=2;
%let x2=4;
%let x3=6;
%let x4=5;

%let s=0;

%macro summation;

%do i=1 %to 4;
    %let s=%eval(&s+&&x&i);
%end;
%put &s;

%mend;
%summation;