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USACO 2022 January Contest, Gold

Problem 3. Tests for Haybales


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Farmer John's cows have decided to offer a programming contest for the cows on Farmer Nhoj's farm. In order to make the problems as fun as possible, they have spent considerable time coming up with challenging input cases. For one problem in particular, "Haybales", the cows need your help devising challenging inputs. This involve solving the following somewhat intriguing problem:

There is an array of sorted integers x1x2xN (1N105), and an integer K. You don't know the array or K, but you do know for each index i, the largest index ji such that xjixi+K. It is guaranteed that iji and j1j2jNN.

Given this information, Farmer John's cows need to construct any array along with some integer K that matches that information. The construction needs to satisfy 0xi1018 for all i and 1K1018.

It can be proven that this is always possible. Help Farmer John's cows solve this problem!

INPUT FORMAT (input arrives from the terminal / stdin):

The first line of input contains N. The next line contains j1,j2,,jN.

OUTPUT FORMAT (print output to the terminal / stdout):

Print K, then x1,,xN on separate lines. Any valid output will be accepted.

SAMPLE INPUT:

6
2 2 4 5 6 6

SAMPLE OUTPUT:

6
1
6
17
22
27
32

The sample output is the array a=[1,6,17,22,27,32] with K=6. j1=2 is satisfied because a2=61+6=a1+K but a3=17>1+6=a1+K, so a2 is the largest element that is at most a1. Similarly,

  • j2=2 is satisfied because a2=66+6 but a3=17>6+6
  • j3=4 is satisfied because a4=2217+6 but a5=27>17+6
  • j4=5 is satisfied because a5=2722+6 but a5=32>22+6
  • j5=6 is satisfied because a6=3227+6 and a6 is the last element of the array
  • j6=6 is satisfied because a6=3232+6 and a6 is the last element of the array

This is not the only possible correct output for the sample input. For example, you could instead output the array [1,2,4,5,6,7] with K=1.

SCORING:

  • For 50% of all inputs, N5000
  • For the remaining inputs, there are no additional constraints.

Problem credits: Danny Mittal

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