function part_1a()


index = linspace(-20,20,41);

for n=1:length(index)
    for k=1:length(index)
        conv(k) =  (heaviside(index(k)) - heaviside(index(k)-6))*(heaviside(index(n)-index(k)) - heaviside(index(n)-index(k)-6));
    end
    conv_sum(n) = sum(conv);
end
stem(conv_sum);