Connectivity — Eolymp

Input

The first line contains two integers $n$ ( $1 \leq n \leq 100$ 1 \leq n \leq 100) — the number of vertices, and $m$ ( $1 \leq m \leq 1 0^{4}$ 1 \leq m \leq 10^4) — the number of edges in the graph. Each of the next $m$ lines contains two integers $u_{i}$ u_i and $v_{i}$ v_i ( $1 \leq u_{i}, v_{i} \leq n$ 1 \leq u_i, v_i \leq n), representing an edge between vertices $u_{i}$ u_i and $v_{i}$ v_i.

Output

Print YES if the graph is connected, otherwise print NO.

Examples

Example 1

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Example 2

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