void take2(int pos, bits &ret) {
ret.set(pos);
for(int i=0;i<N-1;i++) {
if(rela[i].first == pos && !ret.test(rela[i].second)) {
take2(rela[i].second, ret);
}
if(rela[i].second == pos && !ret.test(rela[i].first)) {
take2(rela[i].first, ret);
}
}
}
int go(bits &st) {
if(memo.count(st)) {
return memo[st];
}
bits candi = st;
int cnt = candi.count();
if(cnt == 0) return 1;
for(int i=0;i<N-1;i++) {
int p1 = rela[i].first;
int p2 = rela[i].second;
if(!st.test(p1) || !st.test(p2)) continue;
candi.reset(p2);
}
long long rett = 0;
for(int i=0;i<N;i++) {
if(candi.test(i)) {
long long ret = 1;
int cnt2 = cnt-1;
for(int j=0;j<N-1;j++) {
if(rela[j].first == i) {
bits tmp;
take(rela[j].second, i, tmp);
tmp.set(rela[j].second);
for(int k=0;k<N;k++) {
if(tmp.test(k) && !st.test(k))
tmp.reset(k);
}
int tmp2 = tmp.count();
ret *= combi[cnt2][tmp2];
cnt2 -= tmp2;
ret %= 1000000007;
ret *= go(tmp);
ret %= 1000000007;
}
}
rett += ret;
rett %= 1000000007;
}
}
memo[st] = rett;
}
static inline bool process(bits &was_processed, bits state, val const j,
val const rem, val const d,
char const *const actname, val const lhs, val const rhs) {
if (was_processed.test(j))
return false;
was_processed.set(j);
if (target.test(j)) {
state.set(j);
if (iddfs(state, j, rem - 1, d - 1)) {
result[d].name = actname;
result[d].lhs = lhs;
result[d].rhs = rhs;
return true;
}
return false;
}
action &defrd = deferred[d][defrd_size[d]];
defrd.name = actname;
defrd.lhs = lhs;
defrd.rhs = rhs;
defrd.res = j;
++defrd_size[d];
return false;
}