function f(x)
    exp(x)
end
function M(a,b)
    (b-a)*f((a+b)/2)
end
function L(a,b)
    (b-a)*f(a)
end
function quad(a,b,epsilon)
    yl=L(a,b)
    ym=M(a,b)
    if abs(yl-ym)<epsilon
        return ym
    else
        p=(a+b)/2
        return quad(a,p,epsilon/2)+
               quad(p,b,epsilon/2)
    end
end