class Complex {
  
  // fields
  private double real; // real component
  private double imag; // imaginary component
  
  // constructor
  public Complex(double r, double i) { real = r; imag = i; }
  
  // methods
  public Complex add(Complex other) {
    return new Complex(real+other.real, imag+other.imag);
  }
  
  public String toString() {
    return real+"+"+imag+"i"; // what if imag is neg?
  }
}

public class TestComplex {
  public static void main(String[] args) {
    Complex c1 = new Complex(1,3);
    Complex c2 = new Complex(2,-1);
    System.out.println(c1.add(c2));
  }
}