let n = Int(readLine()!)!
let pr = [2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79]
var x = 2, k = 0, ans = 0
while x <= n{
	ans += 1
	k += 1; x *= pr[k]
}
print(ans)