#include <iostream>
#include <math.h>

using namespace std;

bool isprime(int num, int i, int (&primes)[79000])
{
  for(int j=0;primes[j]<int(sqrt(num)+1);j++)
  {
    if(int(num%primes[j]) == 0)
    {
      return(true);
    }
  }  
  return(false);
}
//---------------------------------------

int main()
{
  int prime = 1;
  double sum =2;
  int i=0;
  int primes[79000];
  primes[0] = 2;
  while(prime < 999998)
  {
    prime+=2;
    i++;     
    while(isprime(prime,i,primes) && prime < 1000000)
    {
      prime+=2;
    }
    if(prime > 1000000)
    {
      break;
    }       
    primes[i] = prime;
    sum+= prime;
  }
  cout.setf(ios::fixed,ios::floatfield);
  cout<<sum<<endl;
  return(0);
}