% order of addition/subtraction
clc
clear
n = 100000;
a = [1:1:n]';
b = -a;
a(1)=a(1) + 1/3;
suma=0;
sumb=0;
sum1 =0;
sum2 = 0;
for i = 1:n
    suma = suma + a(i);
    sumb = sumb + b(i);
    sum1 = sum1 + a(i) + b(i);
end
sum2 = suma + sumb;
[n sum1 sum2]