Average
In college, a student may take several courses. For each course i, he earns a certain credit c[i], and a mark ranging from A to F, which is comparable to a score s[i], according to the following conversion table:
The GPA is the weighted average score of all courses one student may take, if we treat the credit as the weight. In other words,
An additional treatment is taken for special cases. Some courses are based on "Pass/Not pass" policy, where students earn a mark 'P' for "Pass" and a mark 'N' for "Not pass". Such courses are not supposed to be considered in computation. These special courses must be ignored for computing the correct GPA. Specially, if a student’s credit in GPA computation is 0, his/her GPA will be 0.00.
Input
There are several (about 10) test cases. Each test case starts with a line containing one integer n (1 ≤ n ≤ 1000), the number of courses. Then n lines follow, each containing the credit and the mark of one course. Credit is a positive integer less than 10.
Output
For each test case print the GPA, rounded up to two decimal places.