n=float(input())
if 90<=n<=100:
    print("A")
elif 75<=n<=89:
    print("B")
elif 60<=n<=74:
    print("C")
elif 0<=n<=59:
    print("D")
else:
    print("wrong")

a=int(input()) if 100>=a>=90: print("A") elif 89>=a>=75: print("B") elif 74>=a>=60: print("C") elif 59>=a>=0: print("D") else: print("wrong")