function s=newton(x,y,x0)
n=length(x);
for i=1:n
    y1(1,i)=y(i);
end
for i=2:n
    for k=1:(n-i+1)
        y(i,k)=(y(i-1,k+1)-y(i-1,k))/(x(k+i-1)-x(k));
    end
end
t=1;
r=0;
for i=1:n
    for k=1:(i-1)
        t=t*(x0-x(k));
    end
    r=r+y(i,1)*t;
    t=1;
end
s=r;