first_list = []
second_list = []
result = 0
with open("part2_input.txt", "r") as file_input:
    for row in file_input:
        first_column, second_column = map(int, row.split("   "))
        first_list.append(first_column)
        second_list.append(second_column)

for i in first_list:
    result += i * second_list.count(i)

print(result)