| Лимит времени 2000/4000/4000/4000 мс. Лимит памяти 65000/65000/65000/65000 Кб. Prepared by Osman Ay. 
Сложность Альфа
 
 
 Passengers in the TrainShqipA train leaves the first station with N passengers and visits 
K stations before it arrives at the last station. In each station 
some passengers get off the train and others get on the train. 
All the people in the train get off at the last station.
 
 question: Make a program that calculates how many passengers 
get off the train at the last station.
 Input specification:  The first line of the input has two integers K and N where 
0 ≤ (K and N) ≤ 1000. Each of the following K lines contain 
two integers (between 0 and 1000), the first one denotes the 
number of passengers who get off and the second one denotes the 
number of passengers get on the train at that station.
 Output specification:  The output should hava a single integer that is number 
of passengers who get off the train at the last station.
 
| Sample Input I 
 
5 10 10 17
 15 6
 6 6
 8 10
 5 2
 | Sample Input II 
 
8 4 3 7
 8 6
 4 2
 1 3
 4 5
 4 5
 8 6
 6 5
 |  
| Sample Output I 
 
7
 | Sample Output I 
 
5
 |  Для отправки решений необходимо выполнить вход.
 
 
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