(r−l+1)⋅⋅⋅maxl≤i≤r(ai)(r-l+1)···max_{l\leq i\leq r}(a_i)(r−l+1)⋅⋅⋅maxl≤i≤r(ai) 应改为 (r−l+1)×maxl≤i≤r{ai}(r-l+1)\times \max_{l\leq i\leq r}\{a_i\}(r−l+1)×maxl≤i≤r{ai}
$(r-l+1)\times \max_{l\leq i\leq r}\{a_i\}$