LASTDIG  The last digit
Nestor was doing the work of his math class about three days but he is tired of make operations a lot and he should deliver his task tomorrow. His math’s teacher gives him two numbers a and b. The problem consist of finding the last digit of the potency of base a and index b. Help Nestor with his problem. You are given two integer numbers: the base a (0 <= a <= 20) and the index b (0 <= b <= 2,147,483,000), a and b both are not 0. You have to find the last digit of a^{b}.
Input
The first line of input contains an integer t, the number of test cases (t <= 30). t test cases follow. For each test case will appear a and b separated by space.
Output
For each test case output an integer per line representing the result.
Example
Input: 2 3 10 6 2
Output: 9 6
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s_a_k_s_h_a_m:
20180612 12:35:21
use long long and fast modular exponentation for (a^b)%10 

navidator:
20180531 00:31:37
If you get WA and you use modular arithmetic, there could be some issues:


adnanlari:
20180528 22:20:51
giving WA, even after considering all the cases!! 

neverhopeless:
20180420 12:26:36
@narutohokage_1, thanks for the pointer. 

wolv_dhoni:
20180410 07:41:19
It can be solved in O(1), all you have to do is calculate the last digit of a, a^2, a^3, a^4, after that it just keeps on repeating, you can check it on your own. 

flyer2403:
20180322 16:40:33
Last edit: 20180322 16:41:21 

jmr99:
20180311 10:32:34
ac in 2 go !! gys use string and consider 700 b limitation. 

badasshackme:
20180310 15:21:52
700 B limit is annoying. 

venkat016:
20180110 22:31:21
Modular exponenention _/\_ thanks for @ajayc1007 and @prasad_235 

vaibhavcs99:
20171231 08:16:40
AC after two TLE (I was using pow function).Modular exponention does the work.No need to consider when one of them is 0 cases. 
Added by:  Jose Daniel Rodriguez Morales 
Date:  20081201 
Time limit:  1s 
Source limit:  700B 
Memory limit:  1536MB 
Cluster:  Cube (Intel G860) 
Languages:  All except: GOSU 
Resource:  Own 