#include <iostream>
#include <vector>

using namespace std;

struct edge {
	int v;
	int w;
};

int n, m;
int ans = -1;
vector<edge> e[50005];
int in[1505] = { 0 };
bool vis[1505] = { 0 };

void dfs(int now, int sum) {
	if (now == n) {
		ans = max(ans, sum);
		return;
	}
	while (e[now].empty() == false) {
		edge ed;
		ed = e[now].back();
		e[now].pop_back();
		if (vis[ed.v] == true)
			continue;
		vis[ed.v] = true;
		dfs(ed.v, sum + ed.w);
		vis[ed.v] = false;
	}
}

void addedge(int x, int y, int len) {
	edge now;
	in[y]++;
	now.v = y;
	now.w = len;
	e[x].push_back(now);
}

int main() {
	ios::sync_with_stdio(false);
	cin >> n >> m;
	for (int i = 1; i <= m; i++) {
		int a, b, c;
		cin >> a >> b >> c;
		addedge(a, b, c);
	}
	if (in[n] == 0) {
		cout << ans;
		return 0;
	}
	vis[1] = 1;
	dfs(1, 0);
	cout << ans;
	return 0;
}