#!/usr/bin/env python

window = []
inc = 0

with open("input02.txt", "r") as f:
    for line in f:
        num = int(line)
        window.append(num)
        if len(window) < 4:
            continue
        x1 = sum(window[0:3])
        x2 = sum(window[1:4])
        if x1 < x2:
            inc += 1
        window.pop(0) 
	

print(inc)