#!/usr/bin/env python

last = -1
count = 0

with open('input') as f:
    window = []
    for line in f:
        depth = int(line)

        window.append(depth)
        if len(window) < 3:
            continue

        if len(window) > 3:
            window.pop(0)

        cur = sum(window)

        if last > 0 and last < cur:
            count = count +1
        last = cur

print(count)