CF 189 div2 D

D. Psychos in a Linetime limit per test

1 second

Memory limit per test

256 megabytes

Input

Standard input

Output

Standard output

There areNPsychos standing in a line. Each psycho is assigned a unique integer from
1N. At each step every psycho who has an id greater than the psycho to his right (if exists) kills his right neighbor in the line. note that a psycho might kill and get killed at the same
Step.

You're given the initial arrangement of the psychos in the line. calculate how many steps are needed to the moment of time such, that nobody kills his neighbor after that moment. look notes to understand the statement more precise.

Input

The first line of input contains integerNDenoting the number of psychos,
(1 digit ≤ DigitNLimit ≤ limit 10^{5). In the second line there will be a list
NSpace separated distinct integers each in range
1N, Random sive-ids of the psychos in the line from left to right.}

Output

Print the number of steps, so that the line remains the same afterward.

Sample test (s) Input

1010 9 7 8 6 5 3 4 2 1

Output

2

Input

61 2 3 4 5 6

Output

0

Note

In the first sample line of the psychos transforms as follows: [10 9 7 8 6 5 3 4 2 1]
Latency → latency [10 8 4]
Pipeline → pipeline [10]. So, there are two steps.

The breakthrough point of this question is that it can delete the numbers of the following elements, which must be those elements larger than the following element at the beginning, in this way, we can use a queue to store those elements that are larger than the following element in the simulation process. Because an element needs to be deleted, a next array is used to simulate the linked list, which leads to a problem. You must start to delete the element from the back. Otherwise, the next point is incorrect, let the order of team entry at the beginning be reversed.

#include <iostream>#include <cstdio>#include <cstring>#include <cstdio>#include <cstdlib>#include <map>#include <set>#include <vector>#include <queue>#include <stack>#include <algorithm>#include <list>using namespace std;typedef long long LL;typedef pair<int,int> P;const int maxn = 100000 + 5;const int INF = 1000000000;queue<P> Q;int next[maxn];int num[maxn];int main(){    int n;    while(cin >> n){        while(!Q.empty())  Q.pop();        for(int i = 0;i < n;i++){            cin >> num[i];            next[i] = i+1;        }        for(int i = n-2;i >= 0;i--){            if(num[i] > num[i+1]) Q.push(P(i,0));        }        int ans = 0;        while(!Q.empty()){            int pos = Q.front().first;            int round = Q.front().second;            ans = max(ans,round);            Q.pop();            if(next[pos] != n && num[pos] > num[next[pos]]){                next[pos] = next[next[pos]];                Q.push(P(pos,round+1));            }        }        cout << ans << endl;    }    return 0;}