ld l = -1e4, r = 1e4;
    ld x1 = l + (r-l)*phi2;
    ld x2 = r - (r-l)*phi2;
    ld f1 = f(x1, d), f2 = f(x2, d);

    while(r - l > e) {
        if(d == 0) {
            int tmp = 1;
        }
        if(f1 < f2) {
            r = x2;
            x2 = x1;
            f2 = f1;
            x1 = l + (r-l)*phi2;
            f1 = f(x1, d);
        }
        else {
            l = x1;
            x1 = x2;
            f1 = f2;
            x2 = r - (r-l)*phi2;
            f2 = f(x2, d);
        }
    }