**Note: The memory limit for this problem is 512MB, twice the default.**
Bessie has taken on a new job as a train dispatcher! There are two train stations:A and B. Due to budget constraints, there is only a single track connecting the stations. If a train departs a station at time t, then it will arrive at the other station at time t+T(1≤T≤1012).
There are N (1≤N≤5000) trains whose departure times need to be scheduled. The i th train must leave station si at time ti or later (si∈{A,B},0≤ti≤1012). It is not permitted to have trains going in opposite directions along the track at the same time (since they would crash). However, it is permitted to have many trains on the track going in the same direction at the same time (assume trains have negligible size).
Help Bessie schedule the departure times of all trains such that there are no crashes and the total delay is minimized. If train i is scheduled to leave at time ai≥si, the total delay is defined as 
INPUT FORMAT (pipe stdin):
The first line contains N and T.
Then N lines follow, where the ith line contains the station si,
and time ti corresponding to the ith train.
OUTPUT FORMAT (pipe stdout):
The minimum possible total delay over all valid schedules.
SAMPLE INPUT:
1 95
B 63
SAMPLE OUTPUT:
0
The only train leaves on time.
SAMPLE INPUT:
4 1
B 3
B 2
A 1
A 3
SAMPLE OUTPUT:
1
There are two optimal schedules. One option is to have trains 2,3,4 leave on time and train 1 leave after a one-minute delay. Another is to have trains 1,2,3 leave on time and train 4 leave after a one-minute delay.
SAMPLE INPUT:
4 10
A 1
B 2
A 3
A 21
SAMPLE OUTPUT:
13
The optimal schedule is to have trains 1and 3 leave on time, train 2 leave at time 13, and train 4 leave at time 23. The total delay is 0+11+0+2=13.
SAMPLE INPUT:
8 125000000000
B 17108575619
B 57117098303
A 42515717584
B 26473500855
A 108514697534
B 110763448122
B 117731666682
A 29117227954
SAMPLE OUTPUT:
548047356974
SCORING:
Inputs 5-6: N≤15
Inputs 7-10: N≤100
Inputs 11-14: N≤500
Inputs 15-18: N≤2000
Inputs 19-24: No additional constraints
Problem credits: Brandon Wang
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