Addition of two matrix using struct

Im trying to sum two matrix using struct, but it doesnt work.

If this code can be optimized please tell me :D

Compile with:

g++ -O2 -Wall program.cpp -o program

Output:

Proy3.cpp:5:16: error: variable ‘Matrix M1’ has initializer but incomplete type struct Matrix M1 { ^ Proy3.cpp:7:3: error: expected primary-expression before ‘int’ int row, column; ^ Proy3.cpp:7:3: error: expected ‘}’ before ‘int’ Proy3.cpp:7:3: error: expected ‘,’ or ‘;’ before ‘int’ Proy3.cpp:9:2: error: expected declaration before ‘}’ token };

Code:

# include < cstdio >

# include < iostream >

struct Matrix M1 {

    int row, column;
            int x[20][20];
};

struct M2 {

    struct Matrix M1;
        int y[20][20];

};

using namespace std;

int main() {

cout << "Insert size rows: Mat[a]";
cin >> &M1.row);

cout << "Insert size of columns Mat[a]";
cin >> &M1.column;


cout << "Insert size of rows Mat[b]";
cin >> &M2.M1.row;

cout << "Insert size of columns Mat[b]";
cin >> &M2.M1.column;

int i, j;

   // Matrix x

    for(i = 0; i <= M1.row; i++)
{
        for(j = 0; j <= M1.column; j++)
        {
        cout << "Insert number for matrix X : \n";
        cin >> &M1.x[i][j]
        }
}

       // Matrix y

    for(i = 0; i <= M2.M1.row; i++)
{
        for(j = 0; j <= M2.M1.column; j++)
        {
        cout << "Insert number for matrix Y : \n";
        cin << &M2.M1.y[i][j];
        }
}

// Matrix X + Matrix Y

for(i = 0; i <= M1.row; i++)
{
    for(j = 0; j < M1.column; j++)
    {
        cout <<"The sum of " << M1.x[i][j] << " + " <<  M2.M1.y[i][j] << " = " << M1.x[i][j] +  M2.M1.y[i][j] << endl;
    }
}
return 0;

}