小凯有一天突发奇想,写下了一串数字: l(l+1)(l+2)...(r−1)rl(l+1)(l+2)...(r-1)rl(l+1)(l+2)...(r−1)r
这串数字的表达建议改为 l(l+1)(l+2)...(r−1)r ‾\overline{l(l+1)(l+2)...(r-1)r~}l(l+1)(l+2)...(r−1)r