In my program im trying to add the values of a sub-part of my 2d array, a small box of 3 by 3 from a 9 by 9 matrix. Im choosing that small box by the % of rows and columns by 3(modulus 3). (meaning it will take cells like [0][0], [0][3], and so on ) which i want those to be my top right corner of the box and then add 2 more rows and columns making it for instance if we started at [0][0] we will add [0-2][0-2] (3 by 3 box). Im calculating that through a function (as a practice to use functions). The problem is that the program seems to only take in the value of the first cell from that small box, and when i try to loop on the rest of that small box, and add their values, it doesnt take the values correctly (or at all) i want to know if my parameters are wrong, or im giving the function wrong parameters. any help would be appreciated.

//------------including section-----------
#include <iostream>
#include <cstdlib>
//------------using section---------------
using std::cin;
using std::cout;
using std::endl;
//-----our constants and variables---------
const int N=3; //initializing our rows and cols as constants
int counter=0, arr[N*N][N*N];
int sumofrow=0, sumofcol=0,sumsquare=0;
//-------prototypes----------------
void READ_MATRIX(int arr[][N*N]);
bool issquare(int arr[][N*N],int row, int col);
//-------main-------------
int main()
{
    //calling on the function to input our matrix
    READ_MATRIX(arr);

    //checking what functions returned
    if(counter==0)
        cout<<1;
    else
        cout <<0;
    return EXIT_SUCCESS;
}
//-----functions--------
//----readmatrix------
void READ_MATRIX(int arr[][N*N])
{
    for (int row=0; row<N*N; row++)
        for (int col=0; col<N*N; col++) {
            cin >> arr[row][col];
            if (row%3==0&&col%3==0)
                issquare(arr, row, col);
        }
}
//---------issquare-------------
bool issquare(int arr[][N*N],int row, int col)
{
    sumsquare=0;
    for (int r=0;r<3;r++) //trying to loop on values of array
        for (int c=0;c<3;c++)//trying to loop {
            //r+row(because row is passed into the function at 0,3,6)
            //same for col. 
            sumsquare+=arr[r+row][c+col]; // this is where it goes wrong
        }
    //checking to see if sum reached a certain value..
    if (sumsquare==45)
        return true;
    else {
        counter++;
        return false;
    }
}