import numpy as np

l = np.loadtxt("day1.txt")
# l = np.array([[3,4],
            #   [4,3],
            #   [2,5],
            #   [1,3],
            #   [3,9],
            #   [3,3]])

a,b = np.sort(l[:,0]),np.sort(l[:,1])
dist = np.abs(a - b)
tot = np.sum(dist)
# print(tot)

sim = 0
for i in a :
    for j in b :
        if i == j:
            sim += i
print(sim)