function amin=trying(x0,xk1,a,r)
[a,b]=area(x0,xk1,a,r);
yk1=punish(x0,xk1,r);
e=0.00001;
r=0.618;
a1=b-r*(b-a);
a=a1;
y1=subs(yk1);
a2=a+r*(b-a);
a=a2;
y2=subs(yk1);
while(abs((b-a)/b)>=e&&abs((y2-y1)/y2)>=e)
    if(y1>=y2)
        a=a1;
        a1=a2;
        y1=y2;
        a2=a+r*(b-a);
        a=a2;
        y2=subs(yk1);       
    else
        b=a2;
        a2=a1;
        y2=y1;
        a1=b-r*(b-a);
        a=a1;
        y1=subs(yk1);
    end
end
amin=1/2*(a+b);