只有60分，后4个点全wa了

#include<bits/stdc++.h>
#define ll long long
using namespace std;
const int N=4e6+5;
int n,a[N],ans=-1;
int main(){
	cin>>n;
	for(int i=1;i<=n;i++) cin>>a[i];
	int maxx=1,minn=1,l=1,r=1;
	while(1){
		r++;
		if(a[r]>=a[maxx]){
			maxx=r;
			l=minn;
			ans=max(ans,a[maxx]-a[minn]-r+l-1);
		}
		if(a[r]<=a[minn]){
			minn=r;
			l=maxx;
			ans=max(ans,a[maxx]-a[minn]-r+l-1);
		}
		if(r==n) break;
	}
	cout<<ans;
	return 0;
}