function [I,briter]=integralt(a,b,tol)
n=3;
I1=trapez(a,b,n);
n=2*n-1;
I2=trapez(a,b,n);
briter=2;
while(abs(I1-I2)/3>tol)
    I1=I2;
    n=2*n-1;
    I2=trapez(a,b,n);
    briter=briter+1;
end
I=I2;

function I=trapez(a,b,n)
X=linspace(a,b,n);
funkcija;
Y=f(X);
h=X(2)-X(1);
I=(h/2)*(Y(1)+2*sum(Y(2:end-1))+Y(end));