pe10

#include <stdio.h>
#include <math.h>

int main()
{
  int list[2000000] = {2,3}, size=2, n=3, sqrt_n, i;
  long long int acc = 5LL;

  while (1)
  {
    do
    {
      n += 2;
      sqrt_n = sqrt(n);
      for (i=0; i<size && list[i] <= sqrt_n; i++)
      {
        if (n % list[i] == 0) break;
      }
    } while (list[i] <= sqrt_n);

    if (n >= 2000000) break;
    acc += (list[size++] = n);
  }

  printf("sum = %lld\n",acc);
  return 0;
}