#include <bits/stdc++.h>
using namespace std;
template <typename T> using min_priority_queue = priority_queue<T,vector<T>,greater<T>>;

template<typename T>
void printv(vector<T> &v){
    bool b = false;
    for(auto i : v){
        if(b) cout << " ";
        else b = true;
        cout << i;
    }
    cout << endl;
}

template <typename T>
bool chmin(T &a, const T& b) {
    if (a > b) {
        a = b;  // aをbで更新
        return true;
    }
    return false;
}

template <typename T>
bool chmax(T &a, const T& b) {
    if (a < b) {
        a = b;  // aをbで更新
        return true;
    }
    return false;
}

void yn(bool b){
    if(b) cout << "Yes" << endl;
    else cout << "No" << endl;
}

bool debug;
bool randomInput;
void input(){
    if(debug && randomInput){
        
    }
    else{
        
    }
    return;
}

void calc(){
    int N, M;
    cin >> N >> M;
    vector<vector<int>> G(N);
    for(int i = 0; i < M; i++){
        int u, v;
        cin >> u >> v;
        u--; v--;
        G[u].push_back(v);
    }

    vector<int> X = {0, N-2, N-1};
    int INF = 1001002003;
    vector<vector<int64_t>> D(3, vector<int64_t>(3, INF));

    for(int i = 0; i < 3; i++){
        int s = X[i];
        vector<int> d(N, INF);
        d[s] = 0;
        queue<int> q;
        q.push(s);
        while(q.size()){
            int pos = q.front();
            q.pop();
            for(int k : G[pos]){
                if(chmin(d[k], d[pos]+1)){
                    q.push(k);
                }
            }
        }
        for(int j = 0; j < 3; j++){
            D[i][j] = d[X[j]];
        }
    }

    int64_t a1 = D[0][1] + D[1][2] + D[2][0];
    int64_t a2 = D[0][2] + D[2][1] + D[1][0];
    int64_t ans = min(a1, a2);
    if(ans >= INF) ans = -1;
    cout << ans << endl;
    return;
}

int64_t ansSimple;
void calcSimple(){
    return;
}

void calc1(){
    int t; cin >> t;
    for(int i = 0; i < t; i++){
        input();
        calc();
        calcSimple();
    }
}

int main(){
    debug = 0;
    randomInput = 0;
    srand(time(NULL));
    cout << fixed << setprecision(12);
    if(debug){
        calc1();
    }
    else{
        input();
        calc();
    }
    return 0;
}
//