PROGRAMMING:Dijkstra algorithm (template)
For an undirected graph with n (1 ≤ n ≤ 2500) points and m (1 ≤ m ≤ 6200) edges, find the shortest path from s to t.
###Input format:
The first line contains four integers n, m, s and t separated by spaces.
The next M lines are three positive integers per line $$s_{ i}$$、$$t_{ i}$$、$$w_{ i}$$(1≤$$w_{ i} $$= $$10 ^ {9} $$), which means a line from $$s_{ i} $$to $$t_{ i} The length of $$is $$W_{ i} The side of $$.
###Output format:
An integer representing the shortest path length from s to t. Data guarantees that there is at least one path.
###Input example:
```in
7 11 5 4
2 4 2
1 4 3
7 2 2
3 4 3
5 7 5
7 3 3
6 1 1
6 3 4
2 4 3
5 6 3
7 2 1
```
###Output example:
```out
seven
```
###Note:
There may be several directly connected paths between two vertices.
answer：If there is no answer, please comment
###Input format:
The first line contains four integers n, m, s and t separated by spaces.
The next M lines are three positive integers per line $$s_{ i}$$、$$t_{ i}$$、$$w_{ i}$$(1≤$$w_{ i} $$= $$10 ^ {9} $$), which means a line from $$s_{ i} $$to $$t_{ i} The length of $$is $$W_{ i} The side of $$.
###Output format:
An integer representing the shortest path length from s to t. Data guarantees that there is at least one path.
###Input example:
```in
7 11 5 4
2 4 2
1 4 3
7 2 2
3 4 3
5 7 5
7 3 3
6 1 1
6 3 4
2 4 3
5 6 3
7 2 1
```
###Output example:
```out
seven
```
###Note:
There may be several directly connected paths between two vertices.
answer：If there is no answer, please comment