Language: C++

#include<bits/stdc++.h>
using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int> pii;
typedef pair<ll, ll> pll;
typedef pair<ull, ull> pullull;
typedef pair<ll, int> plli;
typedef pair<int, pii> pipii;
typedef vector<vector<int> > mati;
typedef vector<vector<double> > matd;
typedef vector<ll> vll;
typedef vector<vector<ll>> vvll;
typedef vector<vector<vector<ll>>> vvvll;
typedef vector<bool> vb;
typedef vector<vector<bool>> vvb;
typedef vector<vector<vector<bool>>> vvvb;
typedef vector<pll> vpll;

#define FOR(i,x,y) for(ll i=(ll)x; i<(ll)y; ++i)
#define REP(i,y) FOR(i, 0, y)
#define RFOR(i,x,y) for(ll i=(ll)x; i>=(ll)y; --i)
#define RREP(i,x) RFOR(i, x, 0)
#define ALL(a) a.begin(), a.end()
#define pb push_back

inline void IN(void){
  return;
}

template <typename First, typename... Rest>
void IN(First& first, Rest&... rest){
  cin >> first;
  IN(rest...);
  return;
}

inline void OUT(void){
  cout << "\n";
  return;
}

template <typename First, typename... Rest>
void OUT(First first, Rest... rest){
  cout << first << " ";
  OUT(rest...);
  return;
}

template <typename T>
void vec_print(vector<T> VEC){
  REP(i, VEC.size()){
    cout << VEC[i] << " ";
  }
  cout << "\n";
};

template <typename T>
void mat_print(vector<vector<T> > MAT){
  REP(i, MAT.size()){
    REP(j, MAT[i].size()){
      cout << MAT[i][j] << " ";
    }
    cout << "\n";
  }
};

template <typename CLASS1, typename CLASS2>
class HOGE{
  public:
    CLASS1 key;
    CLASS2 value;
    HOGE(void){
      return;
    };
    HOGE(CLASS1 key, CLASS2 value){
      this->key = key;
      this->value = value;
    };
    ~HOGE(void){
      return;
    };

    void print(void){
      cout << "key : " << key << ", value : " << value << "\n";
      return;
    };
    
    bool operator==(const HOGE &obj){
      return (this->value == obj.value);
    };
    bool operator<(const HOGE &obj){
      return (this->value < obj.value);
    };
    bool operator>(const HOGE &obj){
      return (this->value > obj.value);
    };
};

template <typename CLASS1, typename CLASS2>
bool operator==(const HOGE<CLASS1, CLASS2> &hoge1, const HOGE<CLASS1, CLASS2> &hoge2){
  return hoge1.value == hoge2.value;
};

template <typename CLASS1, typename CLASS2>
bool operator<(const HOGE<CLASS1, CLASS2> &hoge1, const HOGE<CLASS1, CLASS2> &hoge2){
  return hoge1.value < hoge2.value;
};

template <typename CLASS1, typename CLASS2>
bool operator>(const HOGE<CLASS1, CLASS2> &hoge1, const HOGE<CLASS1, CLASS2> &hoge2){
  return hoge1.value > hoge2.value;
};

constexpr int INF = (1<<30);
constexpr ll INFLL = 1LL<<62;
constexpr long double EPS = 1e-12;
constexpr ll MOD = (ll)((1E+9)+7);

vvll Path;
vll flag;

void calc(ll init_pos){
  queue<ll> que;
  que.push(init_pos);
  while(!que.empty()){
    ll pos = que.front(); que.pop();
    for(int i=0; i<Path[pos].size(); ++i){
      ll pos1 = Path[pos][i];
      for(int j=0; j<Path[pos1].size(); ++j){
        ll pos2 = Path[pos1][j];
        for(int k=0; k<Path[pos2].size(); ++k){
          ll pos3 = Path[pos2][k];

          if(flag[pos3]>=0) continue;
          flag[pos3] = flag[pos]+1;
          que.push(pos3);
        }
      }
    }
  }
  return;
}

int main(){
  cin.tie(0); // cut the cin and cout (default, std::flush is performed after std::cin)
  ios::sync_with_stdio(false); // cut the iostream and stdio (DON'T endl; BUT "\n";)

  ll N, M;
  IN(N, M);
  Path.resize(N);
  flag.resize(N, -1);
  REP(i, M){
    ll u, v;
    IN(u,v);
    u--; v--;
    Path[u].pb(v);
  }

  Path2.resize(N);

  REP(i, N){
    set<ll> st;
    REP(j, Path[i].size()){
      if(st.find(Path[i][j])!=st.end()) continue;
      st.emplace(Path[i][j]);
    }
    for(auto itr : st){
      Path2[i].pb(itr);
    }
  }

  Path3.resize(N);

  REP(i, N){
    set<ll> st;
    REP(j, Path)
  }

  ll S,T;
  IN(S,T);
  S--; T--;

  flag[S] = 0;

  calc(S);

  if(flag[T]<0){
    OUT("-1");
  }else{
    OUT(flag[T]);
  }

  return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:161:3: error: 'Path2' was not declared in this scope; did you mean 'Path'?
  161 |   Path2.resize(N);
      |   ^~~~~
      |   Path
a.cc:174:3: error: 'Path3' was not declared in this scope; did you mean 'Path'?
  174 |   Path3.resize(N);
      |   ^~~~~
      |   Path
a.cc:21:38: error: invalid cast from type 'vvll' {aka 'std::vector<std::vector<long long int> >'} to type 'll' {aka 'long long int'}
   21 | #define FOR(i,x,y) for(ll i=(ll)x; i<(ll)y; ++i)
      |                                      ^
a.cc:22:18: note: in expansion of macro 'FOR'
   22 | #define REP(i,y) FOR(i, 0, y)
      |                  ^~~
a.cc:178:5: note: in expansion of macro 'REP'
  178 |     REP(j, Path)
      |     ^~~
a.cc:179:3: error: expected primary-expression before '}' token
  179 |   }
      |   ^