// #define DEBUGGING #include using namespace std; #define endl '\n' #define ALL(V) (V).begin(), (V).end() #define ALLR(V) (V).rbegin(), (V).rend() template using V = vector; template using VV = V>; using ll = int64_t; using ull = uint64_t; using PLL = pair; template const T& var_min(const T &t) { return t; } template const T& var_max(const T &t) { return t; } template const T& var_min(const T &t, const Tail&... tail) { return min(t, var_min(tail...)); } template const T& var_max(const T &t, const Tail&... tail) { return max(t, var_max(tail...)); } template void chmin(T &t, const Tail&... tail) { t = var_min(t, tail...); } template void chmax(T &t, const Tail&... tail) { t = var_max(t, tail...); } template const T& clamp(const T &t, const T &low, const T &high) { return max(low, min(high, t)); } template void chclamp(T &t, const T &low, const T &high) { t = clamp(t, low, high); } namespace init__ { struct InitIO { InitIO() { cin.tie(nullptr); ios_base::sync_with_stdio(false); cout << fixed << setprecision(30); } } init_io; } #ifdef DEBUGGING // #include "../debug/debug.cpp" #include "../../debug/debug.cpp" #else #define DEBUG(...) 0 #define DEBUG_SEPARATOR_LINE 0 #endif template T make_v(T init) { return init; } template auto make_v(T init, size_t s, Tail... tail) { #define rec make_v(init, tail...) return V(s, rec); #undef rec } int main() { ll N; cin >> N; V A(N), B(N); for(ll i = 1; i < N; i++) cin >> A[i] >> B[i]; ll sum_a = accumulate(ALL(A), 0ll); ll sum_b = accumulate(ALL(B), 0ll); ll ans = 0; for(ll a = 0; a <= sum_b; a++) { ll b = (sum_a + a) - sum_b; if(b < 0) continue; bool ok = true; for(ll j = 1; j < N; j++) { if(sum_b - B[j] + b < A[j]) ok = false; if(sum_a - A[j] + a < B[j]) ok = false; } ans += ok; } cout << ans << endl; return 0; }