求问各位大神，为什么MFIRST的值是5678呀？？
data one;
input division $ sales;
cards;
A 1234
A 3654
B 5678
;
RUN;
data b;
set one;
by division;
if first.division then call symput("mfirst",sales);
if last.division then call symput("mlast",sales);
%put &mfirst &mlast;
run;