#include<bits/stdc++.h>
using namespace std;
#define INF 1e6
long long book[1501][1501];
long long n, m, ls, lls, q;
int main() {
	cin >> n >> m;
	for (int i = 1; i < n; i++) {
		for (int j = i + 1; j <= n; j++) {
			book[i][j] = INF;
		}
	}
	while (m--) {
		cin >> ls >> lls >> q;
		book[ls][lls] = q * -1;
	}
	for (int k = 2; k < n; k++) {
		for (int i = 1; i < k; i++) {
			for (int j = k + 1; j <= n; j++) {
				book[i][j] = min(book[i][j], book[i][k] + book[k][j]);
			}
		}
	}
	cout << book[1][n] * -1;
	return 0;
}