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Description

Wind Peak Elementary School has the following grading system: scores greater than or equal to 90 are "A", scores greater than or equal to 70 but less than 90 are "B", scores greater than or equal to 60 but less than 70 are "C", and scores below 60 are "D". Given a test score, output its corresponding grade.

Input Format

An integer representing the test score.

Output Format

Output the corresponding grade.

Sample

99

A