문제 예제.

f1 = open('svalue.txt','r',encoding='utf-8')
f2 = open('result.txt','w',encoding='utf-8')
while True:
    data = f1.readline()
    if not data: break
    data = data.split()
    score = int(data[1])
    if score>89:
        data.append('A')
    elif score>79:
        data.append('B')
    elif score>69:
        data.append('C')
    elif score>59:
        data.append('D')
    else:
        data.append('F')
    d = ' '.join(data)
    d = d + '\n'
    f2.write(d)
f1.close()
f2.close()