#include<bits/stdc++.h> #define rep(i,a,b) for(int i=a;i<b;i++) #define rrep(i,a,b) for(int i=a;i>=b;i--) #define fore(i,a) for(auto &i:a) #define all(x) (x).begin(),(x).end() #pragma GCC optimize ("-O3") using namespace std; void _main(); int main() { cin.tie(0); ios::sync_with_stdio(false); _main(); } typedef long long ll; const int inf = INT_MAX / 2; const ll infl = 1LL << 60; template<class T>bool chmax(T &a, const T &b) { if (a<b) { a = b; return 1; } return 0; } template<class T>bool chmin(T &a, const T &b) { if (b<a) { a = b; return 1; } return 0; } //--------------------------------------------------------------------------------------------------- /*--------------------------------------------------------------------------------------------------- ∧_∧ ∧_∧ (´<_` ) Welcome to My Coding Space! ( ´_ゝ`) / ⌒i / \ | | / / ̄ ̄ ̄ ̄/ | __(__ニつ/ _/ .| .|____ \/____/ (u ⊃ ---------------------------------------------------------------------------------------------------*/ int N, A[101], B[101], C[101]; //--------------------------------------------------------------------------------------------------- void _main() { cin >> N; rep(i, 0, N - 1) cin >> A[i]; rep(i, 0, N) cin >> B[i] >> C[i]; int ans = 0, ride = C[0]; rep(i, 0, N - 1) { ans += ride * A[i]; ride -= B[i]; ride += C[i]; } cout << ans << endl; }