Letter Grade

Write letter_grade(score) that converts a numeric score into a letter grade:

• 90 or above: "A"
• 80 to 89: "B"
• 70 to 79: "C"
• 60 to 69: "D"
• below 60: "F"

Examples

Input:  score = 93
Output: "A"

Input:  score = 59
Output: "F"

Input:  score = 80
Output: "B"

Constraints

• 0 <= score <= 100 (may be a float such as 69.5)

Goals

• Chain if/elif/else branches
• Order thresholds from highest to lowest