The shortest path

Улаз

The first line contains two integers $n$ and m~(1 \le n \le 5 \cdot 10^4, 1 \le m \le 10^5) — the number of vertices and edges, respectively.

The second line contains two integers $a$ and $b$ — the starting and ending vertices.

Each of the following $m$ lines describe an edge.

Излаз

If there is no path from $a$ to $b$, print $-1$.

Otherwise, print the length $l$ of the shortest path on the first line, and on the second line print l + 1 numbers: the sequence of vertices along this path.

Примери