n = int(input()) demand = [0] * n price = [0] * n for i in range(n): (demand[i], price[i]) = map(int, input().split()) cumulative_demand = [0] * (n + 1) for i in range(1, n + 1): cumulative_demand[i] = cumulative_demand[i - 1] + demand[i - 1] min_cost = float('inf') for i in range(n): if price[i] < min_cost: min_cost = price[i] for j in range(i + 1, n + 1): if cumulative_demand[j] - cumulative_demand[i] * min_cost < cumulative_demand[j] * price[j - 1]: min_cost = price[j - 1] print(min_cost * cumulative_demand[n])