#define DEBUG 1 #include #include #include #include #include #include #include #include #include #include #include #include #include using namespace std; using ll = long long; using ull = unsigned long long; using ld = long double; using vll = vector; using vvll = vector; using pll = pair; using tll = tuple; #define all(v) (v).begin(), (v).end() #define for1(i, n) for (ll i = 0; i < (n); i++) #define for2(i, m, n) for (ll i = (m); i < (n); i++) #define for3(i, m, n, d) for (ll i = (m); i < (n); i += (d)) #define rfor2(i, m, n) for (ll i = (m); i > (n); i--) #define rfor3(i, m, n, d) for (ll i = (m); i > (n); i += (d)) #define INF 1111111111111111111LL #define MOD 1000000007LL // 10**9 + 7 #define print(...) print_1(__VA_ARGS__) #define in(...) in_1(__VA_ARGS__) #if DEBUG #define dump(...) dump_1(#__VA_ARGS__, __VA_ARGS__) #else #define dump(...) #endif template void dump_1(const char* str, Head&& h) { cerr << str << ": " << h << '\n'; } template void dump_1(const char* str, Head&& h, Tail&&... t) { while (*str != ',') { cerr << *str++; } cerr << ": " << h << ' '; dump_1(str + 1, t...); } template ostream& operator<<(ostream& os, const pair& v) { os << '(' << v.first << ", " << v.second << ')'; return os; } template ostream& operator<<(ostream& os, const tuple& v) { os << '(' << get<0>(v) << ", " << get<1>(v) << ", " << get<2>(v) << ')'; return os; } template ostream& operator<<(ostream& os, const vector& v) { for (auto it = v.begin(); it != v.end(); it++) { if (it != v.begin()) { os << ' '; } os << *it; } return os; } template ostream& operator<<(ostream& os, const set& v) { for (auto it = v.begin(); it != v.end(); it++) { if (it != v.begin()) { os << ' '; } os << *it; } return os; } template ostream& operator<<(ostream& os, const multiset& v) { for (auto it = v.begin(); it != v.end(); it++) { if (it != v.begin()) { os << ' '; } os << *it; } return os; } template ostream& operator<<(ostream& os, const map& v) { os << '{'; for (auto it = v.begin(); it != v.end(); it++) { if (it != v.begin()) { os << ", "; } os << it->first << ':' << it->second; } os << '}'; return os; } void Yes(void) { cout << "Yes" << '\n'; } void No(void) { cout << "No" << '\n'; } void YES(void) { cout << "YES" << '\n'; } void NO(void) { cout << "NO" << '\n'; } template void chmax(T& a, const T& b) { if (a < b) { a = b; } } template void chmin(T& a, const T& b) { if (a > b) { a = b; } } template void vin(vector& v, ll len) { for1 (i, len) { cin >> v[i]; } } template void in_1(Head& h) { cin >> h; } template void in_1(Head& h, Tail&... t) { cin >> h; in_1(t...); } template void print_1(Head&& h) { cout << h << '\n'; } template void print_1(Head&& h, Tail&&... t) { cout << h << ' '; print_1(t...); } //--------------------------------------------------------- void solve() { ll N; in(N); ll as = 0; ll bs = 0; for1 (i, N - 1) { ll a, b; in(a, b); as += a; bs += b; } // A1の最大値はbs // B1の最大値はas ll diff = as - bs; // A1 - B1 = diff ll ans = 0; // dump(diff, bs, as); for1 (i, 1000000) { ll a = i; ll b = a + diff; if (0 <= a && a <= bs && 0 <= b && b <= as) { ans++; } } print(ans); } int main() { ios::sync_with_stdio(false); cin.tie(0); cout << fixed << setprecision(16); cerr << fixed << setprecision(16); solve(); }