how to generate sub-arrays from an array?

#include <iostream>
#include <vector>

using namespace std;

int main() {
  int n = 5;
  int m = 3;
  vector<int> arr = {1, 2, 3, 4, 5};
  int count = 0;

  for (int i = 0; i < n; i++) {
    for (int j = i + 1; j < n; j++) {
      for (int k = j + 1; k < n; k++) {
        if (arr[i] + arr[j] + arr[k] < m) {
          count++;
        }
      }
    }
  }

  cout << count << endl;
  return 0;
}