fuel.py

def main():

    while True:
        try:
            fraction = input('Fraction: ')
            parts = fraction.split('/')
            numer = int(parts[0])
            denom = int(parts[1])
            if numer>denom:
                continue
            pct = round((numer / denom) * 100)
        except ValueError:
            continue
        except ZeroDivisionError:
            continue
        except:
            continue
        else:
            if pct >= 99:
                print('F')
            elif pct <= 1:
                print('E')
            else:
                print(f'{pct}%')
            break

main()