Not the most challenging one, but still:

The sum of the primes below 10 is 2 + 3 + 5 + 7 = 17.

Find the sum of all the primes below two million.

My Solution

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

int isPrime(num){
  int i;
  if (num==2)
    return 1;
  for (i=2;i<sqrt(num)+1;i++){
    if (num%i==0)
      return 0;
    } 
  return 1;
}

int main(){
  int i;
  double soma=0;
  for (i=2;i<2000000;i++){
    if (isPrime(i)==1)
      soma=soma+i;
  }
  printf("%lfn",soma);
  return 0;
}