CCF CSP认证201409-2 画图

n = int(input())
data = list()
for i in range(n):
    x1,y1,x2,y2 = input().split()
    x1,y1,x2,y2 = int(x1), int(y1), int(x2),int(y2)
    for j in range(x1,x2):
        for k in range(y1,y2):
            if [j,k] not in data:
                data.append([j,k])
print(len(data))