#include #define rep(i,n) for (int i = 0; i < n; ++i) #define ALL(c) (c).begin(), (c).end() #define SUM(x) std::accumulate(ALL(x), 0LL) #define MIN(v) *std::min_element(v.begin(), v.end()) #define MAX(v) *std::max_element(v.begin(), v.end()) #define EXIST(v, x) (std::find(v.begin(), v.end(), x) != v.end()) using namespace std; typedef long long ll; template inline bool chmax(T& a, T b) { if (a < b) { a = b; return true; } return false; } template inline bool chmin(T& a, T b) { if (a > b) { a = b; return true; } return false; } const int INF = 1e9; const long long INFL = 1LL<<60; int main() { int n; cin >> n; ll suma = 0; ll sumb = 0; rep(i, n-1) { ll a, b; cin >> a >> b; suma += a; sumb += b; } if (suma < sumb) swap(suma, sumb); // a = b - (suma - sumb) ll ans = 0; for (ll b = suma - sumb; b - (suma - sumb) <= sumb; b++) { ans++; } cout << ans << endl; return 0; }