#include using namespace std; #define incII(i, l, r) for(decay_t i = (l) ; i <= (r); i++) #define incIX(i, l, r) for(decay_t i = (l) ; i < (r); i++) #define incXI(i, l, r) for(decay_t i = (l) + 1; i <= (r); i++) #define incXX(i, l, r) for(decay_t i = (l) + 1; i < (r); i++) #define decII(i, l, r) for(decay_t i = (r) ; i >= (l); i--) #define decIX(i, l, r) for(decay_t i = (r) - 1; i >= (l); i--) #define decXI(i, l, r) for(decay_t i = (r) ; i > (l); i--) #define decXX(i, l, r) for(decay_t i = (r) - 1; i > (l); i--) #define inc(i, n) incIX(i, 0, n) #define dec(i, n) decIX(i, 0, n) #define inc1(i, n) incII(i, 1, n) #define dec1(i, n) decII(i, 1, n) auto inII = [](auto a, auto l, auto r) -> bool { return (l <= a && a <= r); }; auto inIX = [](auto a, auto l, auto r) -> bool { return (l <= a && a < r); }; auto inXI = [](auto a, auto l, auto r) -> bool { return (l < a && a <= r); }; auto inXX = [](auto a, auto l, auto r) -> bool { return (l < a && a < r); }; auto setmin = [](auto & a, auto b) -> bool { return (b < a ? a = b, true : false); }; auto setmax = [](auto & a, auto b) -> bool { return (b > a ? a = b, true : false); }; auto setmineq = [](auto & a, auto b) -> bool { return (b <= a ? a = b, true : false); }; auto setmaxeq = [](auto & a, auto b) -> bool { return (b >= a ? a = b, true : false); }; using LL = long long int; using LD = long double; #define PB push_back #define EB emplace_back #define MP make_pair #define MT make_tuple #define FI first #define SE second #define FR front() #define BA back() #define ALL(a) begin(a), end(a) #define RALL(a) rbegin(a), rend(a) #define RV(a) reverse(ALL(a)) #define ST(a) sort(ALL(a)) #define RST(a) sort(RALL(a)) #define SC static_cast #define SI(a) SC(a.size()) #define SL(a) SC(a.size()) #define RF(e, ...) for(auto && e: __VA_ARGS__) #define SF(a, ...) for(auto && [__VA_ARGS__]: a) #define until(...) while(not(__VA_ARGS__)) #define if_not(...) if(not(__VA_ARGS__)) #define ef else if #define UR assert(false) template istream & operator>>(istream & is, vector & v); template ostream & operator<<(ostream & os, vector const & v); template istream & operator>>(istream & is, array & a); template ostream & operator<<(ostream & os, array const & a); template istream & operator>>(istream & is, pair & p); template ostream & operator<<(ostream & os, pair const & p); template istream & operator>>(istream & is, tuple & t); template ostream & operator<<(ostream & os, tuple const & t); template void tin_ (istream & is, T & t) { if constexpr(I < tuple_size::value) { is >> get(t); tin_(is, t); } } template void tout_(ostream & os, T const & t) { if constexpr(I < tuple_size::value) { if(I != 0) { os << " "; } os << get(t); tout_(os, t); } } template istream & operator>>(istream & is, vector & v) { for(auto && e: v) { is >> e; } return is; } template ostream & operator<<(ostream & os, vector const & v) { string ss; for(auto && e: v) { os << ss << e; ss = " "; } return os; } template istream & operator>>(istream & is, array & a) { for(auto && e: a) { is >> e; } return is; } template ostream & operator<<(ostream & os, array const & a) { string ss; for(auto && e: a) { os << ss << e; ss = " "; } return os; } template istream & operator>>(istream & is, pair & p) { return is >> p.first >> p.second; } template ostream & operator<<(ostream & os, pair const & p) { return os << p.first << " " << p.second; } template istream & operator>>(istream & is, tuple & t) { tin_ (is, t); return is; } template ostream & operator<<(ostream & os, tuple const & t) { tout_(os, t); return os; } auto * IS = & cin; auto * OS = & cout; template void in(A & ... a) { (* IS >> ... >> a); } #define IN(...) __VA_ARGS__; in(__VA_ARGS__) template auto make_v(A a) { return a; } template auto make_v(A a, int n, M ... m) { return vector(n, make_v(a, m ...)); } template auto read_v(N ... n) { auto a = make_v(A { }, n ...); in(a); return a; } void out_([[maybe_unused]] string const & s) { } template void out_([[maybe_unused]] string const & s, A const & a) { * OS << a; } template void out_( string const & s, A const & a, B const & ... b) { * OS << a << s; out_(s, b ...); } auto outF = [](string const & s, string const & t, auto const & ... a) { out_(s, a ...); * OS << t << flush; }; auto outN = [](auto const & ... a) { outF("" , "" , a ...); }; auto outS = [](auto const & ... a) { outF(" " , " " , a ...); }; auto outL = [](auto const & ... a) { outF("\n", "\n", a ...); }; auto outSN = [](auto const & ... a) { outF(" " , "" , a ...); }; auto outNL = [](auto const & ... a) { outF("" , "\n", a ...); }; auto outSL = [](auto const & ... a) { outF(" " , "\n", a ...); }; auto out = outSL; template void disp_(A const & a) { * OS << a; } template void disp_(A const & a, string const & s, T const & ... t) { string ss; for(auto && e: a) { * OS << ss; ss = s; disp_(e, t ...); } } auto dispI = [](auto const & a, auto const & s, auto const & ... t) { disp_(a, t ...); * OS << s << flush; }; auto dispT = [](auto const & a, auto const & s, auto const & ... t) { for(auto && e: a) { disp_(e, t ...); * OS << s; } * OS << flush; }; auto dispL = [](auto const & a, auto const & ... t) { dispT(a, "\n", t ...); }; struct OS_init { OS_init() { * OS << boolalpha << fixed << setprecision(20); } } os_init_; // ---- ---- #define bit(b, i) (((b) >> (i)) & 1) #define PC __builtin_popcountll #define BL(a) (a ? 64 - __builtin_clzll(a) : 0) class Forest { private: int n, B; vector> g, p; vector h, f; vector s; // bool ok; void dfs(int v, int pp, int hh) { if(f[v] != 0) { return; } f[v] = 1; p[v][0] = pp; h[v] = hh; assert(s[v] == 0); s[v] = 1; RF(e, g[v]) { dfs(e, v, hh + 1); } if(v != pp) { s[pp] += s[v]; } } public: Forest(int nn = 0) { init(nn); } void init(int nn) { n = nn; B = 0; while((1 << B) < n) { B++; } g = vector>(n); p = vector>(n, vector(B + 1)); h = vector(n); f = vector(n); s = vector(n); // ok = false; } void add(int a, int b) { assert(! ok); assert(inIX(a, 0, n)); assert(inIX(b, 0, n)); g[a].PB(b); g[b].PB(a); } void calc(const vector & root = { }) { assert(! ok); RF(e, root) { dfs(e, e, 0); } inc(i, n) { dfs(i, i, 0); } inc(k, B) { inc(i, n) { p[i][k + 1] = p[p[i][k]][k]; } } ok = true; } bool same(int a, int b) { assert(ok); assert(inIX(a, 0, n)); assert(inIX(b, 0, n)); return (p[a][B] == p[b][B]); } int lca(int a, int b) { if(! same(a, b)) { return -1; } int d = abs(h[a] - h[b]); if(h[a] > h[b]) { a = up(a, d); } if(h[a] < h[b]) { b = up(b, d); } assert(h[a] == h[b]); if(a == b) { return a; } dec(k, B) { if(p[a][k] != p[b][k]) { a = p[a][k]; b = p[b][k]; } } assert(a != b && p[a][0] == p[b][0]); return p[a][0]; } int dist(int a, int b) { if(! same(a, b)) { return -1; } return h[a] + h[b] - 2 * h[lca(a, b)]; } int up(int a, int x) { assert(ok); assert(inIX(a, 0, n)); if(x > h[a]) { return -1; } inc(k, B) { if(bit(x, k) == 1) { a = p[a][k]; } } return a; } const vector> & get_g() { return g; } const vector> & get_p() { return p; } const vector & get_h() { return h; } const vector & get_s() { return s; } // }; // ---- int main() { int IN(n, q); Forest g(n); inc(i, n - 1) { int IN(a, b); a--; b--; g.add(a, b); } g.calc(); inc(qq, q) { int IN(a, b); a--; b--; auto d = g.get_h(); auto s = g.get_s(); if(d[a] % 2 != d[b] % 2) { out(0); continue; } int c = g.lca(a, b); if(d[a] == d[b]) { int x = d[a] - d[c] - 1; out(n - s[g.up(a, x)] - s[g.up(b, x)]); } else { if(d[a] < d[b]) { swap(a, b); } int x = ((d[a] - d[c]) + (d[b] - d[c])) / 2; out(s[g.up(a, x)] - s[g.up(a, x - 1)]); } } }