# Round #853

## A. Planning¶

Let's for each moment of time use a plane, which can depart in this moment of time (and didn't depart earlier, of course) with minimal cost of delay.

$\text{s.t.} \min \sum_{i=1}^n c_i\cdot(t_i-i) = \sum_{i=1}^n c_i \cdot t_i - \sum_{i=1}^n c_i \cdot i$