data want;
set origin;
tmp=cat(a,b,c,d);
if find(tmp,'small')>=1 and find(tmp,'big')=0 then new="small";
else if find(tmp,'small')=0 and find(tmp,'big')>=1 then new="big";
else if find(tmp,'small')>=1 and find(tmp,'big')>=1 then new="big";
else if find(tmp,'small')=0 and find(tmp,'big')=0 then new="";
run;