Building Teams

input/code.cpp: In function 'void f(int, int)':
input/code.cpp:17:22: error: cannot convert 'std::vector<int>' to 'int' in initialization
   17 |         for (int j : A) {
      |                      ^

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

vector<int> A[200'001];
int Z[200'001];

void f(int i, int z) {
	if (Z[i]) {
		if (Z[i] != z) {
			cout << "IMPOSSIBLE";
			exit(0);
		}
		return;
	}
	Z[i] = z;
	z = z == 1 ? 2 : 1;
	for (int j : A) {
		f(j,z);
	}
}

int main() {
	int n, m;
	cin >> n >> m;
	for (int i = 0; i < m; ++i) {
		int a, b;
		cin >> a >> b;
		A[a].push_back(b);
		A[b].push_back(a);
	}
	for (int i = 0; i < n; ++i) {
		if (!Z[i]) f(i, 1);
	}
	for (int i = 0; i < n; ++i) {
		cout << (Z[i] ? "1 " : "2 ");
	}
}