#include<iostream>
#include<iomanip>
#include<vector>
using namespace std;

int main() 
{
	int x = 0;
	vector<int>count;
	int n;
	while (cin >> n)
	{
		count.push_back(n);
	}
	int len = count.size();
	for (int i = 0; i < len-1; i++)
	{
//		cout << count[i] << endl;
		if (count[i] > count[i + 1])
		{
			x += 1;
		}
	}
	if (x != 0)
	{
		cout << "NO" << endl;
	}
	else
	{
		cout << "YES" << endl;
	}
	return 0;
}
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