# include <cctype>
# include <cstdio>
# include <cstring>
# include <vector>

namespace Main {
    namespace Source {
        typedef short unsigned int hu;
        typedef std::vector<hu> vector;
        static inline const hu min(const hu a, const hu b) { return b < a ? b : a; }
        static inline const void amin(hu& a, const hu b) { a = min(a, b); }
    }
    using namespace Source;
    enum { M = 100, N = 500 };
    static hu m, n;
    static vector bus[M];
    static vector out[N + 1];
    static hu ans[N + 1];
    static inline const void read_bus(vector& bus) {
        char u;
        while (not isdigit(u = getchar()));
        while (true) {
            hu t(0);
            while (t = t * 10 + (u - '0'), isdigit(u = getchar()));
            bus.push_back(t);
            bool brk(false);
            do { if (u == '\n' or u == EOF) { brk = true; break; } }
            while (not isdigit(u = getchar()));
            if (brk) break;
        }
        for (hu i(0); i < bus.size(); ++i) for (hu j(i); j < bus.size(); ++j)
            out[bus[i]].push_back(bus[j]);
    }
    static inline const void main() {
        scanf("%hu%hu", &m, &n);
        for (hu i(0); i < m; ++i) read_bus(bus[i]);
        memset(ans, 0x7f, sizeof ans), ans[1] = 0;
        for (hu i(0); i < n; ++i)
            for (hu j(1); j <= n; ++j)
                for (hu k(0); k < out[j].size(); ++k)
                    amin(ans[out[j][k]], ans[j] + 1);
        if (ans[n] == ans[0]) puts("NO");
        else printf("%hu\n", ans[n] ? ans[n] - 1 : 0);
    }
}

signed int main() { Main::main(); return 0; }

@王乐轩