#include <iostream>
#include <vector>
#include <tuple>
using namespace std;
const int INF = 100001;//别爆 
int main(){
	//dp的分阶段依据总写在最外层(最优子结构和重叠子问题的子问题分段)
	int n, edge_num, start, end;
	cin >> n >> edge_num >> start >> end;
	//相关存储 
	//vector<tuple<int, int, int>> edge(edge_num);
	vector<vector<int>> dp(n, vector<int>(n, INF));
	
	for(int i = 0; i < edge_num; i++){
		int a, b, w;
		cin >> a >> b >> w;
		//edge[i] = {a, b, w};
		dp[a][b] = w;
	}
	
	//dp, 一定把k写最外面 
	for(int k = 0; k < n; k++){
		for(int i = 0; i < n; i++){
			for(int j = 0; j < n; j++){
					dp[i][j] = min(dp[i][j], dp[i][k] + dp[k][j]);
			}
		}
	} 
	for(int k = 0; k < n; k++){
		if(dp[k][k] < 0){
			cout << "Negative Cycle Detected!" << endl;
			return 0;
		}	
	} 
	cout << dp[start][end] << endl;
	return 0;
}