#include<bits/stdc++.h>
using namespace std;
const int N = 1005, INF = 1e5 + 6;
vector <int> p[N], b[N];
queue <int> q;
int n, m, vis[N];
bool cmp[N];
int main() {
	scanf("%d%d", &n, &m);
	for (int i = 1; i <= m; ++i) {
		int x, y, z;
		scanf("%d%d%d", &x, &y, &z);
		p[x].push_back(y);
		b[x].push_back(z);
		p[y].push_back(x);
		b[y].push_back(z);
	}
	cmp[1] = true;
	q.push(1);
	int ans = INF;
	while (!q.empty()) {
		int u = q.front();
		q.pop();
		for (int d = 0; d < p[u].size(); ++d) {
			int nx = p[u][d];
			if (!cmp[nx]) {
				cmp[nx] = true;
				vis[nx] = vis[u] + b[u][d];
				if (nx == n)
					ans = min (ans, vis[nx]);
				q.push(nx);
			}
		}
	}
	printf("%d", ans);
	return 0;
}