#!/usr/bin/env python3

from collections import Counter

list1 = [];
list2 = [];
with open("input.txt") as file:
 for line in file:
  if line.strip():
   num1,num2 = map(int, line.split())
   list1.append(num1)
   list2.append(num2)

counts = Counter(list2)

result = 0;
for num in list1:
 if(counts.get(num)):
  result+=num*counts.get(num)

print(f'Result: {result}')