SDOI2008仪仗队

 1 var i,n,tot:longint;
 2     ans:int64;
 3     phi:array[0..50000] of int64;
 4     p:array[0..50000] of longint;
 5 procedure get;
 6  var i,j:longint;
 7    begin
 8      fillchar(phi,sizeof(phi),0);
 9      tot:=0;
10      phi[1]:=0;
11      for i:=2 to n do
12       if phi[i]=0 then
13        begin
14          phi[i]:=i-1;inc(tot);p[tot]:=i;
15          j:=i+i;
16          while j<=n do
17            begin
18              if phi[j]=0 then phi[j]:=j;
19              phi[j]:=(phi[j] div i)*(i-1);
20              inc(j,i);
21            end;
22        end;
23    end;
24 procedure main;
25  begin
26    readln(n);dec(n);
27    get;
28    for i:=2 to n do inc(phi[i],phi[i-1]);
29    writeln(2*phi[n]+3);
30  end;
31 begin
32   main;
33 end.
34