exited, segmentation fault

The input for this problem is a first number that indicates how many cases will be input to be analyzed.

Input:

3
8 12
9 27
259 111

The first number means that there will be 3 cases. The next 3 lines are the cases. The program has to output the GCD (Greatest Common Divisor) of the 3 cases.

4
9
37

The code I wrote looks like the following:

#include <iostream>
#include <vector>

int gcd(int a, int b) {
   if (b == 0)
      return a;
   return gcd(b, a % b);

}

int main() {

   int N;

   std::cin >> N;

   int i = 0;

   std::vector<int> cards;

   while (i <= N) {
      i++;
      int F1, F2;
      std::cin >> F1 >> F2;
      cards[i] = gcd(F1, F2);
   }

   for (int j; j <= N; i++) {
      i++;
      std::cout << cards[i] << "\n";
   }
}

It reads the first integer (number of test cases), runs the loop once (reads one test case) and stops running. The terminal outputs exited, segmentation fault. What is the problem?