#include <cstdio>

#include <iostream>

#define N 2001

#define max(x, y) ((x) > (y) ? (x) : (y))

int n, tmp;

int a[N], f[N];

inline int read()

{

	int x = 0, f = 1;

	char ch = getchar();

	for(; !isdigit(ch); ch = getchar()) if(ch == '-') f = -1;

	for(; isdigit(ch); ch = getchar()) x = (x << 1) + (x << 3) + ch - '0';

	return x * f;

}

int main()

{

	int i, j;

	while(~scanf("%d", &n))

	{

		for(i = 1; i <= n; i++) a[i] = read();

		for(i = 1; i <= n; i++)

		{

			tmp = 0;

			for(j = i - 1; j >= 1; j--)

				if(a[j] >= a[i])

					tmp = max(tmp, f[j]);

			f[i] = tmp + 1;

			if(f[i] >= 3)

			{

				puts("No!");

				break;

			}

		}

		if(i > n) puts("Yes!");

	}

	return 0;

}