1 #include <stdio.h>
2 #include <queue>
3 #include <string.h>
4 #include <algorithm>
5 #define inf 2000000000
6 using namespace std;
7 typedef pair<long long , int > pii;
8 priority_queue <pii, vector<pii>, greater<pii > > q;
9 struct node
10 {
11 int u, v, w, next;
12 }a[100005];
13 int tot, n, m, rxa, rxc, rya, ryc;
14 int dis[100005];
15 int rp, T, first[100005];
16 int done[100005];
17 void addedge(int st, int end, int val)
18 {
19 a[++tot].u = st;a[tot].v = end;a[tot].w = val;
20 a[tot].next =first[st];first[st] = tot;
21 }
22 int dij()
23 {
24 for (int i = 1; i <= n; i++)dis[i] = inf;
25 q.push(make_pair(0, 1));
26 dis[1] = 0;
27 while (!q.empty())
28 {
29 int u = q.top().second;q.pop();
30 if(done[u])continue;
31 done[u] = 1;
32 for (int e = first[u]; e != -1; e = a[e].next)
33 {
34 int v = a[e].v;
35 if (dis[u] + a[e].w < dis[v])
36 {
37 dis[v] = dis[u] + a[e].w;
38 q.push(make_pair(dis[v], v));
39 }
40 }
41 }
42 }
43 int main()
44 {
45 scanf("%d %d", &m, &n);
46 int x, y;
47 memset(first, -1, sizeof(first));
48 for (int i = 1; i <= m; i++)
49 {
50 scanf("%d %d", &x, &y);
51 addedge(x, y, 1);
52 }
53 dij();
54 if(dis[n] == inf)printf("-1\n");
55 else printf("%d\n", dis[n]+1);
56 return 0;
57 }
