2581 : 소수 [C++]

#include <iostream>
#include <vector>

using namespace std;

int main()
{
 cin.tie(NULL);

 int M, N;
 cin >> M >> N;

 vector<int> Primes;
 int Sum = 0;

 for (int i = M; i <= N; i++)
 {
  bool Flag = false;
  
  if (i == 2 || i == 3)
  {
   Primes.push_back(i);
   continue;
  }
  
  if (i % 2 == 0 || i % 3 == 0 || i == 1)
   continue;
  
  for (int j = 3; j < i; j++)
  {
   if (i % j == 0)
   {
    Flag = true;
    break;
   }
  }
  if (!Flag)
   Primes.push_back(i);
 }

 for (int i = 0; i < Primes.size(); i++)
  Sum += Primes[i];

 if (Primes.size() == 0)
  cout << -1 << "\n";
 else
  cout << Sum << "\n" << Primes[0] << "\n";

 return 0;
}