C++ Array that takes user input for the size and the elements [duplicate]

The prompt is that simple for now.

#include <iostream> using namespace std;const int i = 10;const int j = 10;int arr[i][j];int main(){    cout << "What would you want the size to be? ";    cin >> j;    for (int i; i < j; i++)    {        cout <<     }    return 0;}

I try to make an array that gets each of those values and makes it functional, but it doesn't work.