LCC '18 Contest 4 S3 - Flight Plan

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Points: 7
Time limit: 2.0s
Memory limit: 64M

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Problem types

Howard has recently started a new full-time job which gives him K vacation days to use during the year. He is looking to spend all of his vacation days on a single trip to Hanoi, however he is having a hard time finding a pair of flights that are exactly K days apart.

Given the N flights to and from Hanoi this year, find the minimum cost of two flights A and B such that:

  • A is a flight to Hanoi.
  • B is a flight from Hanoi.
  • A and B are exactly K days apart.

Input Specification

The first line of input contains two integers N, K (1 \le N \le 100\ 000, 1 \le K \le 10^9), the number of flights and the number of vacation days that Howard has.

The next N lines each contain three terms D, T, C describing a flight, where:

  • D (1 \le D \le 10^9) is the day the flight departs.
  • T is either T or F, representing whether the flight is to or from Hanoi, respectively.
  • C (1 \le C \le 10^9) is the cost of the flight.

Output Specification

Output the minimum cost of a pair of flights satisfying the conditions in the problem description, or -1 if no such pair exists.

Sample Input 1

2 3
1 F 1000
4 T 1000

Sample Output 1

-1

Sample Input 2

3 5
1 T 1000
3 T 100
6 F 1000

Sample Output 2

2000

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