#include <iostream> #include <algorithm> #include <vector> using namespace std; int main() { int n; cin >> n; vector<int> a(n); for (int i = 0; i < n - 1; i++) cin >> a[i]; int ans = 0; int curr = 0; for (int i = 0; i < n; i++) { int b, c; cin >> b >> c; curr -= b; curr += c; ans += curr * a[i]; } cout << ans << endl; }