Result in complex

Good morning/evening I wrote this code but the result was in complex form Can any one help to convert the result into real numbers

    clc
  disp('Enter the required information for the fisrt alternative ')
  IntialCostFA=input('Enter the intial cost for the first alternative :   ');
  UACFA=input('Enter the uniform annual cost for the first alternative :   ');
  UABFA=input('Enter the uniform annual benefit for the first alternative :   ');
  SalFA=input('Enter the salvage value for the first alternative :   ');
  UseLifeFA=input('Enter the useful life for the first alternative :   ');

disp('Enter the required information for the second alternative ')
IntialCostSA=input('Enter the intial cost for the second alternative :   ');
UACSA=input('Enter the uniform annual cost for the second alternative :   ');
UABSA=input('Enter the uniform annual benefit for the second alternative :   ');
SalFSA=input('Enter the salvage value for the second alternative :   ');
UseLifeSA=input('Enter the useful life for the second alternative :   ');
r=input('Enter the MARR:     ');

n1=UseLifeFA;
n2=UseLifeSA;
% NPW for Alt A
a=(((1+r)^n2)-1)/(r*((1+r)^n2));
CapRec1=UACFA*a;
PR1=(IntialCostFA-SalFA)*(1+r)^n1;
PWC1=IntialCostFA+CapRec1+PR1;

CapRec2=UABFA*a;
PR2=SalFA*(1+r)^n2;
PWB1=CapRec2+PR2

[Walter Roberson]

What does "MARR" mean in this context?

Can the MARR be negative?

Are all of the inputs scalars, or is it possible that the MARR is a vector?

Note: "a" could also be rewritten as (1-1/(1+r)^n2)/r

For efficiency, it would make sense to only calculate (1+r)^n2 once, assign that to a variable, and use that in the other expressions.

Have you put a breakpoint in at the assignment to n1, and single-stepped through the lines until you found the one that generates the complex value? If so, then which line is it?