#include <iostream>
using namespace std;

void main()
{
    int flag[100][100];
    int flag1[100], N, j, flag2[100];
    do
    {
        cin >> N;
    }
    while (N < 0 || N > 100);

    for (int i = 1; i <= N; i++)
    {
        do
        {
            cin >> j;
            flag[i][j + 1] = 1;
        }
        while (j != 0);
    }
    flag1[1] = 1;
    for (int i = 1; i <= N; i++)
    {
        for (j = i + 1; j <= N; j++)
        {
            if (flag[i][j] == 1)
            {
                if (flag1[j] != 1 && flag1[j] != 2)
                {
                    flag1[j] = 3 - flag1[i];
                }
            }
        }
    }
    int i = 0;
    for (j = 1; j <= N; j++)
    {
        if (flag1[j] == 1)
        {
            flag2[i] = j;
            i++;
        }
    }
    for (j = 0; j < i; j++)
    {
        cout << flag1[i];
    }
}
I have debugged, but finally I can't find why my code gives wrong answers. Anyone help me, plz.