View Code of Problem 4067

#include<iostream>
using namespace std;
long long  a[1000010];
int main() {
	int n;
	cin >> n;
	for (int i = 0; i < n; i++)
		cin >> a[i];
		int flag=0;
	for (int i = n - 1; i >= 1; i--) {
		if (a[i] > a[i - 1]) {
			if((a[i]-1)>=(a[i-1]+1)){
				flag=1;
				break;
			}
			else
			{
				a[i]=a[i]-1;
				a[i-1]=a[i-1]+1;
				
			}
		}
	}
	if(flag==1)
		{
			cout<<"No\n";
			return 0;
		}
	for(int i=0;i<n-1;i++)
	{
		if(a[i]<=a[i+1])
			{
					cout<<"NO\n";
					return 0;
			}
	}
	cout<<"YES\n";
		
}