Author:  Антон Карабанов  Time limit:  1 sec  
Input file:  Standard input  Memory limit:  512 Mb  
Output file:  Standard output 
Oh, those math lessons! Today, for example was the fourth test on the subject. To those who finished ahead of time the teacher offered an extra task for bonus points.
Two ndigit numbers are written on the blackboard, first composed of only the digit d_{1}, second — of only the digit d_{2}. Determine which digit occupies position k in the sum of those numbers. Positions are numbered left to right starting from 1.
You want bonus points, don't you?
Four lines of input contain four integers: n, d_{1}, d_{2} and k. It is guaranteed that k is correct.
Output a single decimal digit — answer to the problem.
1 ≤ n ≤ 10^{9}
1 ≤ k ≤ n + 1
1 ≤ d_{1}, d_{2} ≤ 9
Sample has n = 2 (adding twodigit numbers), d_{1} = 5 (first number is 55), d_{2} = 8 (second number is 88). Sum is 55 + 88 = 143. k = 1 (teacher asks the first digit of the result). The digit at first position of the number 143 is 1.
No.  Standard input  Standard output 

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