uses crt;
var n,i,j:longint;
s:int64;
a:array[1..100000000] of boolean;

begin
clrscr;
readln(n);
fillchar(a,sizeof(a),true);
a[1]:=false;
for i:=1 to trunc(sqrt(n)) do
if a[i] then
begin
 j:=i*i;
 while j<=n do
 begin
  a[j]:=false;
  j:=j+i;
 end;
end;
for i:=2 to n do
 if a[i] then
  s:=s+i;
write(s);
readln
end.

program tong_ngto_be_hon_n;
uses crt;
var n,i,tong:longint;
function ngto(n:longint):boolean;
var i:integer;
begin
    if (n<2) then exit(false); {neu n<2 thi out}
    for i:=2 to trunc(sqrt(n)) do {cho i chay den phan nguyen cua can bac 2 cua n}
    begin
        if n mod i=0 then 
        exit(false);
    end;
    exit(true);
end;
begin
    clrscr;
    tong:=0;
    write('Nhap n: ');readln(n);
    for i:=1 to n-1 do 
    begin 
        if ngto(i) then tong:=tong+i;
    end;
    write('Tong cua cac so nguyen to be hon n la: ',tong);
readln;
end.