Problem A. Elementary arithmetic ≡

Statement

Underwater arithmetic is very elementary. There are just two operations: WITH and WITHOUT which mean addition and subtraction respectively.

Underwater mathematicians did not yet invent brackets, so all expressions are calculated from right to left. For example, the expression 3 WITH 5 WITHOUT 4 WITHOUT 7 is calculated as (3 + (5 − (4 − 7))).

Scientists of Nearsea Institute of Underwater Arithmetic need a program to evaluate such expressions.

Input file format

First line of input file contains a single integer N. Following 2 × N + 1 lines describe the expression. Odd lines contain integer operands, even lines contain operations.

Output file format

Output file must contain a single integer — calculation result.

Constraints

1 ≤ N ≤ 10³

All operands are in range from 0 to 10³.

Sample tests

1
2
WITH
3

5

3
10
WITHOUT
5
WITH
3
WITH
15

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