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 ab.


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.


For each test case output an integer per line representing the result.


3 10
6 2

Output: 9 6

hide comments
abhinav_313: 2018-06-16 21:10:02

how to input multiple strings separated by space.Please help

s_a_k_s_h_a_m: 2018-06-12 12:35:21

use long long and fast modular exponentation for (a^b)%10

navidator: 2018-05-31 00:31:37

If you get WA and you use modular arithmetic, there could be some issues:
1- b must be a string
2- b can be 0, but if b=0 then a != 0.

adnanlari: 2018-05-28 22:20:51

giving WA, even after considering all the cases!!

neverhopeless: 2018-04-20 12:26:36

@narutohokage_1, thanks for the pointer.

wolv_dhoni: 2018-04-10 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: 2018-03-22 16:40:33

Last edit: 2018-03-22 16:41:21
jmr99: 2018-03-11 10:32:34

ac in 2 go !! gys use string and consider 700 b limitation.

badasshackme: 2018-03-10 15:21:52

700 B limit is annoying.

venkat016: 2018-01-10 22:31:21

Modular exponenention _/\_ thanks for @ajayc1007 and @prasad_235

Added by:Jose Daniel Rodriguez Morales
Time limit:1s
Source limit:700B
Memory limit:1536MB
Cluster: Cube (Intel G860)
Languages:All except: GOSU