C++ Matrix Addition and Multiplication

#include <iostream>
using namespace std;

// performs matrix addition and multiplication using class

class matrix {
    int a[10][10], r, c;

public:
    matrix(int x = 0, int y = 0) {
        r = x;
        c = y;
    }

    void input() {
        for (int i = 0; i < r; i++)
            for (int j = 0; j < c; j++)
                cin >> a[i][j];
    }

    void display() {
        for (int i = 0; i < r; i++) {
            for (int j = 0; j < c; j++)
                cout << a[i][j] << " ";
            cout << endl;
        }
    }

    matrix add(matrix m) {
        matrix rs(r, c);
        for (int i = 0; i < r; i++)
            for (int j = 0; j < c; j++)
                rs.a[i][j] = a[i][j] + m.a[i][j];
        return rs;
    }

    matrix mul(matrix m) {
        matrix rs(r, m.c);
        for (int i = 0; i < r; i++) {
            for (int j = 0; j < m.c; j++) {
                rs.a[i][j] = 0;
                for (int k = 0; k < c; k++)
                    rs.a[i][j] += a[i][k] * m.a[k][j];
            }
        }
        return rs;
    }
};

int main() {
    int r1, c1, r2, c2;
    cout << "Enter size A: ";
    cin >> r1 >> c1;
    cout << "Enter size B: ";
    cin >> r2 >> c2;

    matrix A(r1, c1), B(r2, c2);
    cout << "Enter A:\n";
    A.input();
    cout << "Enter B:\n";
    B.input();

    if (r1 == r2 && c1 == c2) {
        cout << "Add:\n";
        A.add(B).display();
    }

    if (c1 == r2) {
        cout << "Mul:\n";
        A.mul(B).display();
    }

    return 0;
}