data export;
        input corp $ country $;
datalines;
A1 C1
A1 C2
A1 C5
A2 C1
A2 C3
A3 C6
A3 C5
A4 C1
;
RUN;

proc sql;
        create table count as
        select country as country, count(distinct corp) as num
        from export
        group by country;
quit;