$dist[v]$表示从$s$出发经过的最大的边取最小
当点$u$松弛操作$v$的时候
$dist[v] = min(dist[v], max(dist[u], w)\quad w为边长$

#include<bits/stdc++.h>
//unordered_map hash
//priority_queue<int,vector<int>,greater<int>>
//deque front back
#define endl '\n'
#define PII pair<int,int>
#define int long long
//#define int __int128
using namespace std;
inline int read();
inline void write(int x);
vector<PII> g[10005];
int dist[10005];
int st[10005];
int n, m, s, t;
void diji(int u){
    priority_queue<PII, vector<PII>, greater<PII>> q;
    memset(dist, 0x3f,sizeof(dist));
    dist[u] = 0;

    q.push({0, u});
    while(q.size()){
        PII t = q.top();
        q.pop();
        int distace = t.first, u = t.second;
        if(st[u]) continue;
        st[u] = 1;
        for(int i = 0; i < g[u].size(); ++ i){
            int v = g[u][i].first, w = g[u][i].second;
            if(dist[v] > max(dist[u], w)){
                dist[v] = max(dist[u], w);
                q.push({dist[v], v});
            }
        }
    }
}
void solve(){
    n = read(), m = read(), s = read(), t = read();
    for(int i = 1; i <= m; ++ i){
        int u = read(), v = read(), w = read();
        g[u].push_back({v, w});
        g[v].push_back({u, w});
    }
    diji(s);
    cout << dist[t];
}
signed main(){
    int _ = 1;
    while(_ --) solve();

    return 0;
}
inline int read(){
    int x=0,f=1;char c=getchar();
    while(c<'0'||c>'9'){
        if(c=='-') f=-1;
        c=getchar();
    }
    while(c>='0'&&c<='9')x=(x<<3)+(x<<1)+c-'0',c=getchar();
    return x*f;
}
inline void write(int x){
    if(x < 0) putchar('-'), x = - x;
    if(x > 9) write(x / 10);
    putchar('0' + x % 10);
}