n, m = map(int, input().split())

cnt_black_row = [0] * n
cnt_black_col = [0] * n

for _ in range(m):
    r, c = map(int, input().split())
    cnt_black_row[r-1] += 1
    cnt_black_col[c-1] += 1

# Case 1: Fix all rows (R[i] = 0), choose optimal C[j]
case1 = 0
for j in range(n):
    case1 += min(n - cnt_black_col[j], cnt_black_col[j])

# Case 2: Fix all columns (C[j] = 0), choose optimal R[i]
case2 = 0
for i in range(n):
    case2 += min(n - cnt_black_row[i], cnt_black_row[i])

print(min(case1, case2))