Dragons

Source: Codeforces

Version: Phuoc Hung OJ Extended

Problem Statement

A player starts with strength $s$ and must defeat $n$ dragons. Dragon $i$ has strength $x_i$ and reward $y_i$. The player wins a duel only if the current strength is strictly greater than $x_i$; after winning, strength increases by $y_i$. Dragons may be fought in any order. Determine whether all dragons can be defeated.

Input

The first line contains $s,n$. Each of the next $n$ lines contains $x_i,y_i$.

Output

Print YES if all dragons can be defeated, otherwise print NO.

Subtasks

General constraints:

• $1 \le s \le 10^4$.

• $1 \le n \le 10^3$.

• $1 \le x_i \le 10^4$.

• $0 \le y_i \le 10^4$.

• Subtask 1 (20 points): $n \le 10$, $x_i,y_i \le 100$

• Subtask 2 (30 points): $n \le 200$

• Subtask 3 (50 points): No additional constraints.

Examples

Input

2 2
1 99
100 0

Output

YES

Explanation

Strength $2>1$, so the first dragon is defeated and strength becomes $101$. Then $101>100$, so the second dragon is also defeated.