int diagonalDifference(vector<vector<int>> arr) {
int sum1 = 0;
int sum2 = 0;
int j = arr.size()-1;
for(int i = 0; i < arr.size(); i++){
    sum1 += arr[i][i];
    sum2 += arr[i][j];
    j--;
}
return abs(sum1-sum2);