#ifdef LOCAL #define _GLIBCXX_DEBUG #define __clock__ #else #pragma GCC optimize("Ofast") #endif #include using namespace std; using ll = long long; using VI = vector; using VV = vector; using VS = vector; using PII = pair; // tourist set template string to_string(pair p); template string to_string(tuple p); template string to_string(tuple p); string to_string(const string& s) { return '"' + s + '"'; } string to_string(const char* s) { return to_string((string) s); } string to_string(bool b) { return (b ? "true" : "false"); } string to_string(vector v) { bool first = true; string res = "{"; for (int i = 0; i < static_cast(v.size()); i++) { if (!first) { res += ", "; } first = false; res += to_string(v[i]); } res += "}"; return res; } template string to_string(bitset v) { string res = ""; for (size_t i = 0; i < N; i++) { res += static_cast('0' + v[i]); } return res; } template string to_string(A v) { bool first = true; string res = "{"; for (const auto &x : v) { if (!first) { res += ", "; } first = false; res += to_string(x); } res += "}"; return res; } template string to_string(pair p) { return "(" + to_string(p.first) + ", " + to_string(p.second) + ")"; } template string to_string(tuple p) { return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " + to_string(get<2>(p)) + ")"; } template string to_string(tuple p) { return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " + to_string(get<2>(p)) + ", " + to_string(get<3>(p)) + ")"; } void debug_out() { cerr << '\n'; } template void debug_out(Head H, Tail... T) { cerr << " " << to_string(H); debug_out(T...); } #ifdef LOCAL #define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__) #else #define debug(...) 42 #endif // tourist set end templatebool chmax(T &a, const T &b) { if (abool chmin(T &a, const T &b) { if (b()) #define MP make_pair ll SUM(VI& V){ return accumulate(ALL(V), 0LL); } void print_vector(VI& V){ ll n = V.size(); rep(i, n){ if(i) cout << ' '; cout << V[i]; } cout << endl; } ll gcd(ll a,ll b){ if(b == 0) return a; return gcd(b,a%b); } ll lcm(ll a,ll b){ ll g = gcd(a,b); return a / g * b; } void no(){p_no(); exit(0);} void yes(){p_yes(); exit(0);} const ll mod = 1e9 + 7; const ll inf = 1e18; const double PI = acos(-1); int main(){ cin.tie(0); ios::sync_with_stdio(false); // input ll N; cin>>N; VI A(2*N); rep(i, 2*N) cin >> A[i]; VI V; for(int i=0; i<2*N; i+=2){ ll a = A[i]; ll b = A[i+1]; V.push_back(a-b); } debug(V); ll sum = SUM(V); debug(sum); ll ma = sum; for(int i=N-1; i>=0; i--){ // i番目をひっくり返す sum -= 2*V[i]; chmax(ma, sum); } p(ma); return 0; }