include

int main() {
int n;
std::cout << "Enter the size of the matrix: ";
std::cin >> n;

int A[n][n];
for (int i = 0; i < n; i++) {
for (int j = 0; j < n; j++) {
if (i == j) {
A[i][j] = i;
} else {
A[i][j] = 0;
}
}
}
std::cout << "Matrix A:" << std::endl;
for (int i = 0; i < n; i++) {
for (int j = 0; j < n; j++) {
std::cout << A[i][j] << " ";
}
std::cout << std::endl;
}
return 0;

}