program demxau;
uses crt;
var s : string;       
i,count : integer;
beginclrscr;
write('Nhap xau: ');
readln(s);​
count:=0;
for i:=1 to Length(s) dobegins[i]:=Upcase(s[i]);
if (s[i] = 'S' ) then count:=count+1;
end;
write('So ki tu S trong xau: ',count);
readln;
end.