program trungbinhngto;
uses crt;
var n,i,d,j:integer;
t:longint;
kt:boolean;
begin
clrscr;
write('Nhap N= '); readln(n);
t:=0; d:=0;
for i:=2 to n do
begin
kt:=true;
for j:=trunc(sqrt(i)) do
if i mod j=0 then kt:=false;
if kt=true then
begin
t:=t+i;
d:=d+1;
end;
end;
write('Trung binh cong so nguyen to nho hon hoac bang ',n,' la: ',t/d:2:1;
readln
end.