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

# 坐标编号
idx = [[0] * (n + 1) for _ in range(m + 1)]

tt = 0
for i in range(m + 1):
    for j in range(n + 1):
        idx[i][j] = tt
        tt += 1


cnt, ans = 0, 0

fa = list(range((m + 1) * (n + 1) + 1))

def father(x):
    if fa[x] == x: return x
    fa[x] = father(fa[x])
    return fa[x]

# 读取必需边
import sys

for line in sys.stdin:
    x1, y1, x2, y2 = map(int, line.split())

    fx1, fx2 = father(idx[x1][y1]), father(idx[x2][y2])
    if fx1 != fx2:
        fa[fx1] = fx2
        cnt += 1

# 竖向连接边
for i in range(1, m):
    for j in range(1, n + 1):

        fx1, fx2 = father(idx[i][j]), father(idx[i + 1][j])
        if fx1 == fx2: continue
        fa[fx1] = fx2
        ans += 1
        cnt += 1

# 横向连接边
for i in range(1, m + 1):
    for j in range(1, n):
        fx1, fx2 = father(idx[i][j]), father(idx[i][j + 1])
        if fx1 == fx2: continue
        fa[fx1] = fx2
        ans += 2
        cnt += 1

print(ans)