dp dfs

#include <bits/stdc++.h>
#define INF 1e9+123
#define f first
#define s second
#define pb push_back
#define loop(x, n) for (int i = x; i < n; i++)
#define bloop(x, n) for (int i = n; i >= x; i--)
using namespace std;
using ll = long long;

vector<vector<pair<ll, ll>>> g;
vector<ll> dp;
vector<int> used, ans;
int n, m, s, t;

void dfs(ll u) {
    used[u] = 1;
    for (auto to : g[u]) {
        ll v = to.f;
        if(to.f == t){
            return;
        }
        if (used[v] == 0) {
            dfs(v);
        }

    }
    // dp[i] = min(dp[to.f]) + W;
    ll minn = INF, mq = -1;
    if(g[u].empty()){
        minn = 0;
    }
    for(auto to : g[u]){
        minn = min(minn, dp[to.f]);
        if (minn == dp[to.f]) {
            mq = to.f;
        }
    }
    if(mq == -1){
        dp[u] = 0;
    }else{
        dp[u] = minn + g[u][mq].s;
    }


    ans.pb(u);
}
void solve() {
    cin >> n >> m >> s >> t;
    //ans.resize(n);
    g.resize(n);
    used.assign(n, 0);
    dp.assign(n, INF);
    loop(0, m) {
        int a, b, w;
        cin >> a >> b >> w;
        a--, b--;

        g[a].pb({b, w});
    }
    dfs(s);
    cout << dp[s];


}

int main() {
#ifdef DEBUG


#else
#endif // DEBUG
    solve();

    return 0;
}