C++ :

#include<bits/stdc++.h>
using namespace std;
long long n,s,m,t,a[5000005];
int main()
{
    cin>>n;a[1]=1;
    for(int i=2;i*i<=n;i++)
        if(a[i]==0)
          for(int j=2*i;j<=n;j+=i)
              a[j]++;
    for(int i=1;i<=n;i++)
    { 
    	m=sqrt(i);
    	if(a[i]==0)t+=i;
    	else 
    	{
    	   for(int j=2;j<=m;j++)
    	   if(i%j==0)
		   {
			  t+=j;
			  break;
		   }
	    }
	}
	cout<<t;
    return 0;
}

Pascal :

const
  maxn=2000000;
  inf='common.in';
  ouf='common.out';
var
  a:array[0..maxn+1] of longint;
  i,j,s,k,n,m:longint;
  ans:int64;
begin
{assign(input,inf);
  assign(output,ouf);
  reset(input);
 rewrite(output);}
  readln(n);
  k:=2;
  s:=0;
  while k<=n do
    begin
      s:=k;
      while s<=n do
        begin
          if a[s]=0
            then begin
                   a[s]:=k;
                   ans:=ans+k;
                 end;
          s:=s+k;
        end;
      while a[k]<>0 do k:=k+1;
    end;
  writeln(ans);
{close(input);
 close(output);}
end.