n = int(input())
x = 0
for i in range(1900, n + 1):
    if((i % 4 == 0) and (i % 100 != 0)) or (i % 400 == 0):
        x += 1
print(x)
/**************************************************************
	Problem: 1749
	User: admin
	Language: Python
	Result: Accepted
	Time:112 ms
	Memory:34244 kb
****************************************************************/