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
amish1999: 2020-05-18 15:00:57

Here we only need to calculate (a^b)mod 10 with the help of modular exponentiation.

Last edit: 2020-05-18 15:05:57
avi_kumar15: 2020-05-17 19:37:34

700B lol

elucidase: 2020-05-17 14:18:37

Euclid theorem gives cycle 4 for coprime numbers; others you can check, also with period 4.

meher_24: 2020-05-10 22:26:45

this little judge doesnt like pow function guys.Nothing is wrong with ur code people.

amar_shukla1: 2020-05-08 12:15:31

easy problem
just use binary exponentiation or method of periodicity(as 2^1=1,2^2=4,2^3=8,2^4=16,2^5=32...)And this period goes on.

kuldeepkarhana: 2020-04-29 10:16:58

just use binary exponention with mod 10 that's it.

satwikmishra1: 2020-04-26 13:18:12

good problem,consider the cases when a or b might be 0 and yes,AVOID if else statements,check 700 bit constrains and yes please consider switching lines while printing the output.

saddy_2001: 2020-04-23 20:44:50

use fast exponentiation !

abhishek_251: 2020-04-17 21:14:51

at most you have to make 4 multiplications to get the answer :) just find the pattern only.

s_cube98: 2020-02-21 20:29:13

The constraints made this one interesting tho!!

Last edit: 2020-02-21 22:07:23

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