#include <iostream> using namespace std; int main() { int n, buy, cool, cost = 0, min_fish = 1e9; cin >> n; for (int i = 0; i < n; ++i) { cin >> buy >> cool; min_fish = min(min_fish + (i>0 ? cool : 0), buy); cost += (i==0 ? buy : min_fish); } cout << cost; }