program trungbinh;
uses crt;
var m,n,i,d:integer;
t:longint;
begin
clrscr;
repeat
write('Nhap m: '); readln(m);
write('Nhap n: '); readln(n);
if m>=n then writeln('m phai be hon n. Nhap lai!');
until (m<n);
d:=0; t:=0;
i:=m;
while i<=n do
begin
d:=d+1;
t:=t+i;
i:=i+1;
end;
write('Trung binh cong cac so tu ',m,' den ',n,' la: ',t/d:2:2);
readln;
end.