#define X_SIZE 60
#define Y_SIZE 30

int matrix[X_SIZE][Y_SIZE];

void init_matrix(void)
{
    register int *matrix_ptr;

    for (matrix_ptr = &matrix[0][0]; 
             matrix_ptr <= &matrix[X_SIZE-1][Y_SIZE-1];
             matrix_ptr++) {

        *matrix_ptr = -1;
    }
}


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