testscore = int(input("What percent did the student achieve? "))    
while testscore < 0 or testscore > 100:
    testscore = int(input("What percent did the student achieve? "))
   
if testscore >= 80:
    grade = "A"
elif testscore >= 70:
    grade = "B"
elif testscore >= 60:
    grade = "C"
elif testscore >= 50:
    grade = "D"
elif testscore >= 40:
    grade = "E"
else:
    grade = "U"
    
print("A percentage of " + str(testscore) +" gains you a grade " + grade)