could u pleas help me to run this code ?

sympref('HeavisideAtOrigin',1);

syms t toe

f1 = heaviside(toe) - heaviside(toe-1);

f2 = heaviside(t-toe) - heaviside(t-toe-1);

conv_ans = int(f1*f2,toe,-inf,inf);

fplot(conv_ans,[-1 3])

i couldnt plot it!!