C++ :

#include <iostream> 
#include <cstdio>
#include <cstring>
#define foru(i, l, r) for (int i = l; i <= r; i ++)
using namespace std; 

const int N = 510;
int m, n, e[N][N], a[N];
bool vst[N];

void dijkstra() {
	vst[1] = true;
	
	foru (i, 2, n) {
		int t = 0;
		foru (j, 1, n) {
			if (!vst[j] && e[1][j] < e[1][t]) t = j;
		}
		vst[t] = true;
		
		foru (j, 1, n) {
			if (!vst[j]) e[1][j] = min(e[1][j], e[1][t]+e[t][j]);
		}
	}
}

int main() {
	scanf("%d%d\n", &m, &n);
 	memset(e, 0x3f, sizeof(e));
 	
 	while (m--) {
 		int num = 0, cnt = 0;
 		char ch;
 		while (scanf("%c", &ch)) {
			if (ch>='0' && ch<='9') {
				num = num*10 + ch-'0';
			}
			else {
				a[++cnt] = num;
				num = 0;
 				if (ch == '\n') break;
			}
		}
		
 		foru (i, 1, cnt) {
 			foru (j, i+1, cnt) {
 				e[a[i]][a[j]] = 1;
			}
 		}
	}
	
	dijkstra();
	
	if (e[1][n] == 0x3f3f3f3f) cout << "NO";
	else cout << e[1][n] - 1;
	
	return 0;
}