цикл

#include <iostream>
#include <vector>
#include <cmath>
using namespace std;



vector<vector<int>>B1;
int lelus,it;

bool kekus(int a){
    if(a == it){
        return true;
    }
    if (a == 0){
        return false;
    }
    for(int i = 0;i < lelus; ++i){
        if(B1[i][0] == a){
            return kekus(B1[i][1]);
        }
    }
    return false;
}








int main(){
    int a,b,d = 0;
    cin>>a;
    vector<vector<int>>A(a,vector<int>(a,0));



    for(int i = 0;i < a; ++i){
        for(int h = 0; h < a; ++h){
            cin>>b;
            A[i][h] = b;
        }
    }



    for(int i = 0;i < a; ++i){
        for(int h = 0; h < a; ++h){
            if(A[i][h] == 1){
                d+=1;
                if(A[h][i] == 1){
                    cout<<"1"<<endl;
                    return 0;
                }
            }
        }
    }



    vector<vector<int>>B(d);
    int c = 0;


    for(int i = 0;i < a; ++i){
        for(int y = 0; y < a ; ++y){
            if(A[i][y]==1){
                B[c].push_back(i);
                B[c].push_back(y);
                c+=1;
            }

        }
    }



    B1 = B;
    lelus = d;



    for(int i = 0;i < d; ++i){
        it = B[i][0];
        if (kekus(B[i][1])){
            cout<<"1"<<endl;
            return 0;
        }
    }
    cout<<"0";
    cout<<endl;
    return 0;
}