f3= @(x) sin(pi*x);
I3=1/pi;

deltax=1e-6;
blad=1;
N=1;
M=1;
a=0;
b=1/2;
n=0;
while blad > deltax

    n=n+1;
   KW(n)=0;
   x=linspace(a,b,M+1);
   for k=1:(length(x)-1)
       KW(n)=KW(n)+(x(k+1)-x(k))*(1/2*f3(x(k))+1/2*f3(x(k+1)));
   end
   blad=abs(KW(n)-I3);
   Nw(n)=M+1;
   M=M*3;

end
M/3