Given an undirected connected graph with $n$ vertices and $m$ edges, find the second shortest path from $1$ to $n$. The length of this path must be greater than the shortest path.
### Input
- The first line contains two integers $n$ and $m$.
- The next $m$ lines each contain three integers $u$, $v$, and $w$, indicating a path of length $w$ between $u$ and $v$.
### Output
- Print an integer representing the length of the second shortest path.
### Constraints
- $1 \le n, m \le 10^5$.
- $1 \le u, v \le n$.
- $1 \le w \le 10^4$.
### Example
Input:
```
4 4
1 2 100
2 4 200
2 3 250
3 4 100
```
Output:
```
450
```
