Elastic collisions

0.60

You have a billiard pool LL units long and 1 unit wide, and nn identical billiard balls of diameter 1, labeled from left to right with the numbers 1, 2, …, nn. Initially, all balls are at integer positions, and the ball 1 is at the very left (at the position 11). After striking the ball 1, it moves to the right, with a speed of 1 unit per second. Supposing that the collisions (between the balls as well as against right and left walls) are completely elastic, and that there is no friction, at which position will a given ball be at a given second?

  0.40

(140,170) (13.5,155)1 (25.5,155)2 (37.5,155)3 (49.5,155)4 (61.5,155)5 (73.5,155)6 (85.5,155)7 (97.5,155)8 (109.5,155)9 (121.5,155)10 (133.5,155)11

(9,151)(1,0)134 (9,136)(1,0)134 (9,131)(1,0)134 (9,116)(1,0)134 (9,111)(1,0)134 (9,96)(1,0)134 (9,91)(1,0)134 (9,76)(1,0)134 (9,71)(1,0)134 (9,56)(1,0)134 (9,51)(1,0)134 (9,36)(1,0)134 (9,31)(1,0)134 (9,16)(1,0)134 (9,11)(1,0)134 (9,-4)(1,0)134

(9,151)(0,-1)15 (9,131)(0,-1)15 (9,111)(0,-1)15 (9,91)(0,-1)15 (9,71)(0,-1)15 (9,51)(0,-1)15 (9,31)(0,-1)15 (9,11)(0,-1)15

(143,151)(0,-1)15 (143,131)(0,-1)15 (143,111)(0,-1)15 (143,91)(0,-1)15 (143,71)(0,-1)15 (143,51)(0,-1)15 (143,31)(0,-1)15 (143,11)(0,-1)15

(2,143.5)(1,0)8 (14,123.5)(1,0)8 (26,103.5)(1,0)8 (50,83.5)(1,0)8 (86,63.5)(1,0)8 (98,43.5)(1,0)8 (122,23.5)(1,0)8 (138,3.5)(-1,0)8

(16,143.5)(13.5,140)1 (52,143.5)(49.5,140)2 (76,143.5)(73.5,140)3 (88,143.5)(85.5,140)4 (124,143.5)(121.5,140)5

(28,123.5)(25.5,120)1 (52,123.5)(49.5,120)2 (76,123.5)(73.5,120)3 (88,123.5)(85.5,120)4 (124,123.5)(121.5,120)5

(40,103.5)(37.5,100)1 (52,103.5)(49.5,100)2 (76,103.5)(73.5,100)3 (88,103.5)(85.5,100)4 (124,103.5)(121.5,100)5

(40,83.5)(37.5,80)1 (64,83.5)(61.5,80)2 (76,83.5)(73.5,80)3 (88,83.5)(85.5,80)4 (124,83.5)(121.5,80)5

(40,63.5)(37.5,60)1 (64,63.5)(61.5,60)2 (76,63.5)(73.5,60)3 (100,63.5)(97.5,60)4 (124,63.5)(121.5,60)5

(40,43.5)(37.5,40)1 (64,43.5)(61.5,40)2 (76,43.5)(73.5,40)3 (112,43.5)(109.5,40)4 (124,43.5)(121.5,40)5

(40,23.5)(37.5,20)1 (64,23.5)(61.5,20)2 (76,23.5)(73.5,20)3 (112,23.5)(109.5,20)4 (136,23.5)(133.5,20)5

(40,3.5)(37.5,0)1 (64,3.5)(61.5,0)2 (76,3.5)(73.5,0)3 (112,3.5)(109.5,0)4 (124,3.5)(121.5,0)5

Input

Input consists of several cases. Each case begins with LL and nn, followed by the nn positions of the balls. All the positions are different, between 11 and LL, and one of them is 1. Then comes q1q\ge 1, the number of queries about this case, followed by qq pairs of integer numbers ii and tt. Assume 1n1041 \le n \le 10^4, n<L106n < L \le 10^6, 1in1 \le i \le n, and 0t1080 \le t \le 10^8.

Output

For each pair of ii and tt, print the position of the ball with label ii at the second tt, following the format of the example. Print an empty line after the output for each case.

Problem information

Author: Unknown
Translator: Carlos Molina

Generation: 2026-01-25T10:11:54.820Z

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