uses crt;
var f:text; i,n,d:longint; a:array[1..20]of longint; tb:real;
begin
clrscr;
for i:=1 to 20 do
begin
write('Nhap phan tu thu ',i,': ');readln(a[i]);
tb:=tb+a[i];
end;
assign(f,'output.pas');rewrite(f);
write(f,'a. ');
for i:=1 to 20 do
if a[i]>50 then write(f,a[i],' ');
writeln(F); tb:=tb/20;
writeln(f,'b. ',tb:0:2);
for i:=1 to 20 do
if a[i]>tb then inc(d);
writeln(f,'c. ',d);
close(f);
readln
end.