写的 $\operatorname{Bellman-Ford}$，不知道为啥错了。

#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
const int INF = 0x3f3f3f3f;
const int N = 5e4 + 10;
int dis[N]; 
struct edge {
	int u, v, w; 
}e[2 * N];
int n, m, s, t;

void ford() {
	for (int i = 1; i <= n; i++) {
		for (int j = 1; j <= m; j++) {
			if (dis[e[i].v] < dis[e[i].u] + e[i].w) {
				dis[e[i].v] = dis[e[i].u] + e[i].w;
			}
		}
	}
}

int main() {
	cin >> n >> m;
	for (int i = 1; i <= n; i++) {
		dis[i] = -INF;
	} 
	for (int i = 1; i <= m; i++) {
		cin >> e[i].u >> e[i].v >> e[i].w;
	}
	dis[1] = 0;
	ford();
	if (dis[n] == -INF) {
		cout << -1;
		return 0;
	}
	cout << dis[n];
	return 0;
}