#!/usr/bin/env python3

file = [int(i.rstrip()) for i in open("input").readlines()]

count = 0
for i in range(len(file)):
    try:
        firstwindowsum = file[i] + file[i + 1] + file[i + 2]
        secondwindowsum = file[i + 1] + file[i + 2] + file[i + 3]
    except IndexError:
        break

    if secondwindowsum > firstwindowsum:
        count += 1

print(count)