#include <stdio.h>
const int SIZE= 30005, MAXX=2000000000;
int n,m,tail, dist[SIZE];
bool mark[SIZE];
struct Node
{
int id, val;
Node* next;
}node[SIZE];
struct Heap{
int id, val;
}heap[2*SIZE];
void insert(int a, int b, int val)
{
Node* p = new Node;
p->id = a;
p->val = val;
p->next = node[b].next;
node[b].next = p;
}
void heappush(int id, int val)
{
heap[++tail].id = id;
heap[tail].val = val;
int child, parent, temp;
child = tail;
while((parent = child/2)>=1)
{
if(heap[child].val < heap[parent].val) // child's val < parent's val ; swap ,filter
{
temp = heap[child].id;
heap[child].id = heap[parent].id;
heap[parent].id = temp;
temp = heap[child].val;
heap[child].val = heap[parent].val;
heap[parent].val = temp;
child = parent;
}
else
break;
}
}
int heappop()
{
int child, parent, temp,ret;
ret = heap[1].id;
heap[1].id = heap[tail].id; 

// swap the tail to the root
heap[1].val = heap[tail--].val;
parent = 1;
while((child=2*parent)<=tail)
{
if(child+1<=tail && heap[child+1].val < heap[child].val)
child++;
if(heap[child].val<heap[parent].val)
{
temp = heap[child].id;
heap[child].id = heap[parent].id;
heap[parent].id = temp;
temp = heap[child].val;
heap[child].val = heap[parent].val;
heap[parent].val = temp;
parent = child;
}
else
break;
}
return ret;
}
int dijkstra(int s, int t)
{
int i;
for(i=1; i<=n; i++)
{
dist[i] = MAXX;
mark[i] = false;
}
Node* p;
p = node[s].next;
while(p)
{
dist[p->id] = p->val;
heappush(p->id, p->val);
p = p->next;
}
mark[s] = true; dist[s] = 0;
for(i=1; i<n; i++)
{
int pop = heappop();
while(mark[pop])
pop = heappop();
if(pop ==t || dist[pop]==MAXX)	break;
mark[pop] = true;
p = node[pop].next;
while(p)
{

if(!mark[p->id]&&

(dist[p->id]==MAXX || dist[pop]+p->val< dist[p->id]))
{
dist[p->id] = dist[pop] + p->val;
heappush(p->id, dist[p->id]);
}
p = p->next;
}
}
return dist[t];
}
int main()
{
int i,a,b,c;
scanf("%d%d", &n, &m);
for(i=1; i<=m; i++)
{
scanf("%d%d%d", &a, &b, &c);
insert(a, b, c);
}
printf("%d\n", dijkstra(n,1));
return 0;
}