PROBLEM : Given data about users, action and time of action, convert the given data in a table like format into a structure that can help identify customer dropoff.
You can use any data structure for input and output.

INPUT DATA
ID. TIME ACTION
100 1000 A
200 1000 A
100 1100 B
200 1150 B
200 1200 C
100 1200 A
300 1500 B
300 1600 B
400 1700 B

EXPECTED OUTPUT
A (2)
-> B (2)
-> C (1)
-> A (1)
B (2)
-> B (1)