#include <bits/stdc++.h>
using namespace std;
long long NumberOfMaps (int N, int M, int *A, int *B) {
vector<vector<int>> g(N + 1);
for (int i = 0; i < M; ++i) {
g[max(A[i], B[i])].push_back(min(A[i], B[i]));
}
int res = 0;
vector<int> color(N + 1, 0);
function<void(int)> backtrack = [&](int i) {
if (i > N) {
// for (int i = 1; i <= N; ++i) cerr << color[i] << " \n"[i == N];
++res;
return;
}
for (int j = 1; j <= 4; ++j) {
bool ok = true;
for (int x : g[i]) if (color[x] == j) ok = false;
if (!ok) continue;
color[i] = j;
backtrack(i + 1);
}
};
backtrack(1);
return res;
}
