MCCME 3581

{$APPTYPE CONSOLE}
{$R+,S+,Q+,I+,C+,M+,H+,O+}
{R+,S-,Q+,I-,C-,M-,H-,O+}

uses
    SysUtils, Math;

var
    i, qq : longint;
    n, q, s, f, ls, lf : int64;
    x, y : array[0..100010] of extended;
    d, dd : array[0..100010] of extended;
    p : array[0..100010, 1..2] of extended;
    ans, ys, yf : extended;

function dst(y1, y2 : extended) : extended;
begin
    result := max(y2 - y1, 0);
end;

function find(xx : int64) : int64;

var
    l, r, c : int64;

begin
    l := 1;
    r := n;
    while r - l > 1 do begin
        c := (l + r) shr 1;
        if x[c] > xx then r := c else l := c;
    end;
    if x[r] <= xx then result := r else result := l;
end;

function getY(l : int64; x : extended) : extended;
begin
    if l > n then result := y[n] else result := p[l][1] * x + p[l][2];
end;

begin
    reset(input, 'input.txt');
    rewrite(output, 'output.txt');
    read(n);
    for i := 1 to n do
        read(x[i], y[i]);
    x[n + 1] := x[n] + 10;
    y[n + 1] := y[n] + 10;
    d[1] := 0;
    for i := 2 to n do begin
        d[i] := d[i - 1] + dst(y[i - 1], y[i]);
        p[i][1] := (y[i] - y[i - 1]) / (x[i] - x[i - 1]);
        p[i][2] := (y[i - 1] * x[i] - x[i - 1] * y[i]) / (x[i] - x[i - 1]);
    end;
    dd[n] := 0;
    for i := n - 1 downto 1 do
        dd[i] := dd[i + 1] + dst(y[i + 1], y[i]);
    read(q);
    for qq := 1 to q do begin
        read(s, f);
        ls := find(s);
        lf := find(f);
        ys := getY(ls + 1, s);
        yf := getY(lf + 1, f);
        if s = f then ans := 0 else
        if s < f then
            if ls = lf then ans := dst(ys, yf) else ans := d[lf] - d[ls + 1] + dst(ys, y[ls + 1]) + dst(y[lf], yf)
        else
      if ls = lf then ans := dst(ys, yf) else ans := dd[lf + 1] - dd[ls] + dst(ys, y[ls]) + dst(y[lf + 1], yf);
        writeln(ans:0:16);
    end;
end.