f = open('input.txt', 'r')
input = f.readlines()
count = 0
for i in range(len(input)):
    input[i] = input[i].strip()
    input[i] = int(input[i])
for x in range(len(input) - 3):
    a = input[x] + input[x + 1] + input[x + 2]
    b = input[x + 1] + input[x + 2] + input[x + 3]
    if a < b:
        count += 1
print(count)