CF963E.Circles of Waiting

普及/提高-

通过率:0%

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题目描述

A chip was placed on a field with coordinate system onto point (0,0)(0,0) .

Every second the chip moves randomly. If the chip is currently at a point (x,y)(x,y) , after a second it moves to the point (x1,y)(x-1,y) with probability p1p_{1} , to the point (x,y1)(x,y-1) with probability p2p_{2} , to the point (x+1,y)(x+1,y) with probability p3p_{3} and to the point (x,y+1)(x,y+1) with probability p4p_{4} . It's guaranteed that p1+p2+p3+p4=1p_{1}+p_{2}+p_{3}+p_{4}=1 . The moves are independent.

Find out the expected time after which chip will move away from origin at a distance greater than RR (i.e. will be satisfied).

输入格式

First line contains five integers R,a1,a2,a3R,a_{1},a_{2},a_{3} and a4a_{4} ( 0<=R<=50,1<=a1,a2,a3,a4<=10000<=R<=50,1<=a_{1},a_{2},a_{3},a_{4}<=1000 ).

Probabilities pip_{i} can be calculated using formula .

输出格式

It can be shown that answer for this problem is always a rational number of form , where .

Print PQ1P·Q^{-1} modulo 109+710^{9}+7 .

输入输出样例

  • 输入#1

    0 1 1 1 1
    

    输出#1

    1
  • 输入#2

    1 1 1 1 1
    

    输出#2

    666666674
  • 输入#3

    1 1 2 1 2
    

    输出#3

    538461545

说明/提示

In the first example initially the chip is located at a distance 00 from origin. In one second chip will move to distance 11 is some direction, so distance to origin will become 11 .

Answers to the second and the third tests: and .

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