/*Accepted    2396K    532MS    C++    1363B    2012-08-06 15:32:00*/
#include<cstdio>
#include<cstring>
#include<cstdlib>const int inf = 0x3f3f3f3f;
const int V = 30005;
const int E = 150005;
int pnt[E], cost[E], nxt[E];
int head[V], e, dist[V];
bool vis[V];int relax( int u, int v, int c)
{if( dist[v] > dist[u] + c) {dist[v] = dist[u] + c;return 1;}return 0;
}void addedge( int u, int v, int c)
{pnt[e] = v; cost[e] = c; nxt[e] = head[u]; head[u] = e ++;
}int SPFA( int src, int n)
{int i;for(i = 1; i <= n; ++ i){vis[i] = false; dist[i] = inf;}dist[src] = 0;int S[E], top = 1;S[0] = src; vis[src] = true;while(top) {int u, v;u = S[ --top]; vis[u] = false;for(i = head[u]; i != -1; i = nxt[i]) {v = pnt[i];if( 1 == relax( u, v, cost[i]) && !vis[v]) {S[ top ++] = v; vis[v] = true;}}}return dist[n];
}int main()
{int n, m;while( scanf( "%d%d", &n, &m) == 2){int a, b, c;e = 0;memset( vis, false, sizeof vis);memset( head, -1, sizeof head);while( m --){scanf( "%d%d%d", &a, &b, &c);addedge( a, b, c);}printf( "%d\n", SPFA( 1, n));}return 0;
}

/*Accepted    2392K    610MS    C++    1376B    2012-08-06 15:27:31*/
#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#include<queue>
using namespace std;const int MAXN = 30030, MAXM = 150150;
const int inf = 0x3f3f3f3f;
int first[MAXN], next[MAXM], v[MAXM], w[MAXM], dist[MAXN];
int n, m, e;
typedef pair<int, int> pii;void addedge(int a, int b, int c)
{v[e] = b, w[e] = c;next[e] = first[a], first[a] = e ++;
}void ReadGraph()
{int a, b, c;e = 0;memset(first, -1, sizeof first);while(m --){scanf("%d%d%d", &a, &b, &c);addedge(a, b, c);}
}int Dijkstra(int src, int n)
{int i, x;pii u;priority_queue<pii, vector<pii>, greater<pii> > q;for(i = 1; i <= n; i ++) dist[i] = inf;dist[src] = 0;q.push(make_pair(dist[src], src));while(!q.empty()){u = q.top(), q.pop();x = u.second;if(dist[x] != u.first) continue;if(n == x) break;for(i = first[x]; i != -1; i = next[i]){if(dist[v[i]] > dist[x] + w[i]){dist[v[i]] = dist[x] + w[i];q.push(make_pair(dist[v[i]], v[i]));}}}return dist[n];
}int main()
{while(scanf("%d%d", &n, &m) == 2){ReadGraph();printf("%d\n", Dijkstra(1, n));}return 0;
}