#10(6.5 sec): http://odz.sakura.ne.jp/projecteuler/index.php?cmd=read&page=Problem%2010

def calc(N):
    sum = 2
    primes = [2]
    for i in range(3, N):
        isPrime = True
        for p in primes:
            if i%p==0: isPrime = False; break
            elif p * p > i: break
        if isPrime: primes.append(i); sum+=i
    return sum

print(calc(2000000))