uses crt;
var n,i,dem:byte;
a:array[1..100] of longint;
tong:longint;
begin
clrscr;
write('nhap N:');readln(n);
writeln('nhap N so:');
for i:=1 to n do
begin
write('a[',i,']=');readln(a[i]);
end;
dem:=0; tong:=0;
for i:=1 to n do
begin
if (a[i]>10) and (a[i]<20) then
begin
dem:=dem+1;
tong:=tong+a[i];
end;
end;
if dem=0 then write('khong co so lon hon 10 va nho hon 20');
readln;
end.
chuc ban hoc tot