Help limiting my Monte Carlo Solution

Hello,

I have to write a code to determine a Monte Carlo solution for a PDE problem. The range goes from zero to pi and the limiting factor is the sin wave. My problem that i am experiencing is that my current code stops at on and not the limit of the sin wave. Can someone take a look at the code and see where i made my mistake?

   clear; clc;

n = 1000;
x = linspace(0,1,n);
Xinside = [];
dist_X = [];

figure(1)
clf;
syms p 
bc = sin (p);
Range = [0 pi];
h = ezplot(bc,Range);
hold on

distance = zeros(0,1,n);

for t = 1:n
    a = 0;
    b = 1;
    Xn = a + b*rand();
    Xn(t) = (Xn + Xn)<=1;
    plot(Xn);
    %distance(t) = sum(distance(1:t) <=1);
    %est_pi = 4*Xinside(1:t)./(1:t);
    %plot(est_pi);
    ylabel('estimation')
    xlabel('iteration')
end
hold off