How can i include repeating and complex roots within my code ?

Displayed below is a set code that is meant to solve linear second order homogeneous differential equations where the user is prompted to include 3 coefficients and two intial conditions. I have been tasked to "complete" this code by allowing the roots to be complex and repeated as solutions generated originate from 2 real distinct roots. Any support into how i can alter this code to fit these requirements are greatly appreciated.

c1='Please enter a value for coefficient 1 ';
a=input(c1);
c2='Please enter a value for coefficient 2 ';
b=input(c2);
c3='Please enter a value for coefficient 3 ';
c=input(c3);

intial1='Enter initial condition for the solution' ;
ytime0=input(intial1);

intial2='Enter initial condition of the derivative of solution' ;
ydtime0=input(intial2);


fprintf('The values entered: \n a = %d \n b = %d \n c = %d\n', a,b,c);
response=(b.^2)-(4*a*c);
disp(response)

  if(response>0)
    clc();
    disp('The response is over-damped')

    m1=(-b+sqrt(response))./(2*a);
    m2=(-b-sqrt(response))./(2*a);
    fprintf(' The roots of the characteristic equation \n m1 = %d \n m2 = %d \n', m1, m2);
    D=[1 1;m1 m2];
    F=[ytime0;ydtime0];
    sol=inv(D)*F;
    cons1=sol(1);
    cons2=sol(2);
  
      if (m1>m2)
        tau=1/m1;
        fprintf('the value is %d\n',tau)
      end

      if (m1<m2)
        tau=1/m2;
        fprintf('the value is %d\n',tau)
      end

    time5=7*abs(tau);
    disp(time5)
    t=linspace(0,time5);
    y=cons1*exp(m1*t)+cons2*exp(m2*t);
    plot(t,y)
  end

if(response==0)
disp('The response is critically-damped')
end

if(response<0)
disp('The response is underdamped')
end

Answer 1

[Walter Roberson]

m1 = randn() + 1i*randn();
m2 = randn() + 1i*randn();
fprintf(' The roots of the characteristic equation \n m1 = %d \n m2 = %d \n', m1, m2);

 The roots of the characteristic equation 
 m1 = -1.235814e+00 
 m2 = -6.350351e-01 

The %d format should only be used for integers that have no imaginary part.

MATLAB does not have any % format item for complex numbers: you have to break them into real and imaginary part. However, you can take shortcuts such as

fprintf(' The roots of the characteristic equation \n m1 = %s \n m2 = %s \n', string(m1), string(m2));

 The roots of the characteristic equation 
 m1 = -1.2358+0.74685i 
 m2 = -0.63504-0.72677i