Use Sum value by variable to calculate additional information

[dht115]

Hello, 

I want to sum by variable and use that sum value to calculate additional variable. 

In following dataset, I need to do sum for var1, which is 10. I need to add this sum value to create var2. 

var2 = sum + var1

Input dataset: 

 Final result should be: 

DATA have;
	input group $ var1;
	datalines;
	A 1
	B 2
	C 3
	D 4
;
RUN;

PROC SUMMARY DATA=have;
   var var1;
	output out=have1 (DROP = _TYPE_ _FREQ_) sum=;
RUN;

DATA want;
	set have1;
	rename var1 = var2;
RUN;

[PaigeMiller · Accepted solution]

PROC SUMMARY DATA=have;
   var var1;
   output out=have1 (DROP = _TYPE_ _FREQ_) sum=sum_values;
RUN;
data want; 
    if _n_=1 then set have1;
    set have;
    var1=var1+sum_values;
run;