// clang-format off #ifdef _LOCAL #include #else #include #define cerr if (false) cerr #define debug_bar #define debug(...) #define debug2(vv) #define debug3(vvv) #endif using namespace std; using ll = long long; using ld = long double; using str = string; using P = pair; using VP = vector

; using VVP = vector; using VC = vector; using VS = vector; using VVS = vector; using VI = vector; using VVI = vector; using VVVI = vector; using VLL = vector; using VVLL = vector; using VVVLL = vector; using VB = vector; using VVB = vector; using VVVB = vector; using VD = vector; using VVD = vector; using VVVD = vector; #define FOR(i,l,r) for (ll i = (l); i < (r); ++i) #define RFOR(i,l,r) for (ll i = (r)-1; (l) <= i; --i) #define REP(i,n) FOR(i,0,n) #define RREP(i,n) RFOR(i,0,n) #define FORE(e,c) for (auto&& e : c) #define ALL(c) (c).begin(), (c).end() #define SORT(c) sort(ALL(c)) #define RSORT(c) sort((c).rbegin(), (c).rend()) #define MIN(c) *min_element(ALL(c)) #define MAX(c) *max_element(ALL(c)) #define COUNT(c,v) count(ALL(c),(v)) #define len(c) ((ll)(c).size()) #define BIT(b,i) (((b)>>(i)) & 1) #define PCNT(b) ((ll)__builtin_popcountll(b)) #define LB(c,v) distance((c).begin(), lower_bound(ALL(c), (v))) #define UB(c,v) distance((c).begin(), upper_bound(ALL(c), (v))) #define UQ(c) do { SORT(c); (c).erase(unique(ALL(c)), (c).end()); (c).shrink_to_fit(); } while (0) #define END(...) do { print(__VA_ARGS__); exit(0); } while (0) constexpr ld EPS = 1e-10; constexpr ld PI = acosl(-1.0); constexpr int inf = (1 << 30) - (1 << 15); // 1,073,709,056 constexpr ll INF = (1LL << 62) - (1LL << 31); // 4,611,686,016,279,904,256 template void input(T&... a) { (cin >> ... >> a); } void print() { cout << '\n'; } template void print(const T& a) { cout << a << '\n'; } template void print(const pair& a) { cout << a.first << " " << a.second << '\n'; } template void print(const T& a, const Ts&... b) { cout << a; (cout << ... << (cout << ' ', b)); cout << '\n'; } template void cout_line(const vector& ans, int l, int r) { for (int i = l; i < r; i++) { if (i != l) { cout << ' '; } cout << ans[i]; } cout << '\n'; } template void print(const vector& a) { cout_line(a, 0, a.size()); } template bool chmin(S& a, const T b) { if (b < a) { a = b; return 1; } return 0; } template bool chmax(S& a, const T b) { if (a < b) { a = b; return 1; } return 0; } template T SUM(const vector& A) { return accumulate(ALL(A), T(0)); } template vector cumsum(const vector& A, bool offset = false) { int N = A.size(); vector S(N+1, 0); for (int i = 0; i < N; i++) { S[i+1] = S[i] + A[i]; } if (not offset) { S.erase(S.begin()); } return S; } template string to_binary(T x, int B = 0) { string s; while (x) { s += ('0' + (x & 1)); x >>= 1; } while ((int)s.size() < B) { s += '0'; } reverse(s.begin(), s.end()); return s; } template ll binary_search(const F& is_ok, ll ok, ll ng) { while (abs(ok - ng) > 1) { ll m = (ok + ng) / 2; (is_ok(m) ? ok : ng) = m; } return ok; } template double binary_search_real(const F& is_ok, double ok, double ng, int iter = 90) { for (int i = 0; i < iter; i++) { double m = (ok + ng) / 2; (is_ok(m) ? ok : ng) = m; } return ok; } template using PQ_max = priority_queue; template using PQ_min = priority_queue, greater>; template T pick(stack& s) { assert(not s.empty()); T x = s.top(); s.pop(); return x; } template T pick(queue& q) { assert(not q.empty()); T x = q.front(); q.pop(); return x; } template T pick_front(deque& dq) { assert(not dq.empty()); T x = dq.front(); dq.pop_front(); return x; } template T pick_back(deque& dq) { assert(not dq.empty()); T x = dq.back(); dq.pop_back(); return x; } template T pick(PQ_min& pq) { assert(not pq.empty()); T x = pq.top(); pq.pop(); return x; } template T pick(PQ_max& pq) { assert(not pq.empty()); T x = pq.top(); pq.pop(); return x; } template T pick(vector& v) { assert(not v.empty()); T x = v.back(); v.pop_back(); return x; } int to_int(const char c) { if (islower(c)) { return (c - 'a'); } if (isupper(c)) { return (c - 'A'); } if (isdigit(c)) { return (c - '0'); } assert(false); } char to_a(const int i) { assert(0 <= i && i < 26); return ('a' + i); } char to_A(const int i) { assert(0 <= i && i < 26); return ('A' + i); } char to_d(const int i) { assert(0 <= i && i <= 9); return ('0' + i); } ll min(int a, ll b) { return min((ll)a, b); } ll min(ll a, int b) { return min(a, (ll)b); } ll max(int a, ll b) { return max((ll)a, b); } ll max(ll a, int b) { return max(a, (ll)b); } ll mod(ll x, ll m) { assert(m > 0); return (x % m + m) % m; } ll ceil(ll a, ll b) { if (b < 0) { return ceil(-a, -b); } assert(b > 0); return (a < 0 ? a / b : (a + b - 1) / b); } ll floor(ll a, ll b) { if (b < 0) { return floor(-a, -b); } assert(b > 0); return (a > 0 ? a / b : (a - b + 1) / b); } ll powint(ll x, ll n) { assert(n >= 0); if (n == 0) { return 1; }; ll res = powint(x, n>>1); res *= res; if (n & 1) { res *= x; } return res; } pair divmod(ll a, ll b) { assert(b != 0); ll q = floor(a, b); return make_pair(q, a - q * b); } ll bitlen(ll b) { if (b <= 0) { return 0; } return (64LL - __builtin_clzll(b)); } ll digitlen(ll n) { assert(n >= 0); if (n == 0) { return 1; } ll sum = 0; while (n > 0) { sum++; n /= 10; } return sum; } ll msb(ll b) { return (b <= 0 ? -1 : (63 - __builtin_clzll(b))); } ll lsb(ll b) { return (b <= 0 ? -1 : __builtin_ctzll(b)); } // -------------------------------------------------------- // clang-format on int main() { ios::sync_with_stdio(false); cin.tie(nullptr); cout << fixed << setprecision(15); ll N; input(N); VLL A(N + 1), B(N + 1); REP (i, N) { input(A[i + 1], B[i + 1]); } auto sa = cumsum(A); auto sb = cumsum(B); VLL L, R; RFOR (i, 1, N + 1) { ll prv = B[i] * (sa[N] - sa[i]); ll nxt = A[i] * (sb[N] - sb[i]); if (prv < nxt) { R.push_back(i); } else { L.push_back(i); } } reverse(ALL(R)); VLL P; while (len(L)) { P.push_back(pick(L)); } while (len(R)) { P.push_back(pick(R)); } ll ans = 0; ll sum_b = 0; REP (p, N) { auto i = P[p]; ans += sum_b * A[i]; sum_b += B[i]; } print(ans); return 0; }