1. #include<set>
2. #include<map>
3. #include<queue>
4. #include<ctime>
5. #include<array>
6. #include<cmath>
7. #include<string>
8. #include<bitset>
9. #include<vector>
10. #include<random>
11. #include<chrono>
12. #include<cstring>
13. #include<cassert>
14. #include<complex>
15. #include<cstdio>
16. #include<cstdlib>
17. #include<iostream>
18. #include<algorithm>
19. #include <unordered_set>
20. #include <unordered_map>
21.  
22. // define some stuffs
23. #define inf 0x3f
24. #define EPS 1.0e-4
25. #define maxD 10000
26. #define BUF_SZ 1 << 15
27. #define COSO 100000000
28. #define PI 3.1415926535897932384626433832795
29.  
30. #define fi first
31. #define se second
32. #define pii pair<int, int>
33. #define piii pair<pii, int>
34. #define sz(x) (int)(x).size()
35. #define all(x)  (x).begin(), (x).end()
36.  
37. #define ll long long
38. #define ll long long
39. #define ld long double
40. #define ull unsigned long long
41.  
42. #define pub push_back
43. #define pob pop_back
44. #define puf push_front
45. #define pof pop_front
46.  
47. #define MASK(i) (1LL<<(i))
48. #define BIT(x,i) (((x)>>(i))&1)
49. #define ALL(v) (v).begin(),(v).end()
50. #define __builtin_popcount __builtin_popcountll
51.  
52. using namespace std;
53.  
54. // Set up some constants
55. const int sll = 20;
56. const int sz1 = 1e5 + 15;
57. const int sz2 = 1e6 + 15;
58. const int sz3 = 1e7 + 15;
59. const int MOD1 = 1e7 + 5;
60. const int MOD2 = 1e9 + 5;
61. const int d4i[4] = {-1, 0, 1, 0};
62. const int d4j[4] = {0, 1, 0, -1};
63. const int d8i[8]={-1, -1, 0, 1, 1, 1, 0, -1};
64. const int d8j[8]={0, 1, 1, 1, 0, -1, -1, -1};
65.  
66. // some necessary functions
67. inline namespace Input {
68. int pos, len;
69. char buf[BUF_SZ];
70.  
71. char next_char() {
72.  if (pos == len) {
73.   pos = 0;
74.   len = (int)fread(buf, 1, BUF_SZ, stdin);
75.   if (!len) {
76.    return EOF;
77.   }
78.  }
79.  return buf[pos++];
80. }
81.  
82. int read_int() {
83.  int x;
84.  char ch;
85.  int sgn = 1;
86.  while (!isdigit(ch = next_char())) {
87.   if (ch == '-') {
88.    sgn *= -1;
89.   }
90.  }
91.  x = ch - '0';
92.  while (isdigit(ch = next_char())) {
93.   x = x * 10 + (ch - '0');
94.  }
95.  return x * sgn;
96. }
97. }
98.  
99. inline namespace Output {
100. char buf[BUF_SZ];
101. int pos;
102.  
103. void flush_out() {
104.  fwrite(buf, 1, pos, stdout);
105.  pos = 0;
106. }
107.  
108. void write_char(char c) {
109.  if (pos == BUF_SZ) {
110.   flush_out();
111.  }
112.  buf[pos++] = c;
113. }
114.  
115. void write_int(int x) {
116.  static char num_buf[100];
117.  if (x < 0) {
118.   write_char('-');
119.   x *= -1;
120.  }
121.  int len = 0;
122.  for (; x >= 10; x /= 10) {
123.   num_buf[len++] = (char)('0' + (x % 10));
124.  }
125.  write_char((char)('0' + x));
126.  while (len) {
127.   write_char(num_buf[--len]);
128.  }
129.  write_char('\n');
130. }
131.  
132. void init_output() { assert(atexit(flush_out) == 0); }
133. }
134.  
135. int read() {
136.  int s = 0, f = 1; char ch = getchar();
137.  for(; ch < '0' || ch > '9'; ch = getchar()) if (ch == '-')  f = 1;
138.  for(; '0' <= ch && ch <= '9'; ch = getchar()) s = s * 10 + ch - '0';
139.  return s * f;
140. }
141.  
142. void write(int x) {
143.     if (x >= 10)
144.         write(x / 10);
145.     putchar (x % 10 + '0');
146. }
147.  
148. void BoostCompile(void) {
149.  ios_base::sync_with_stdio(false);
150.  cin.tie(NULL); cout.tie(NULL);
151. }
152.  
153. void SetUpFile&#40;void&#41; {
154.  freopen("NAME.inp", "r", stdin);
155.  freopen("NAME.out", "w", stdout);
156. }
157.  
158. /* Author : Trần Vũ Hải Đăng */
159. const int N = 1e6 + 15;
160.  
161. long long n, kq = 0;
162. bool check[N];
163.  
164. void sieve() {
165.     memset(check, true, sizeof(check));
166.     check[0] = false;
167.     check[1] = false;
168.     for(int i = 2; i * i <= N; ++i) {
169.         if (check[i] == true) {
170.             for(int j = i * i; j <= N; j += i) {
171.                 check[j] = false;
172.             }
173.         }
174.     }
175. }
176.  
177. void Solution(void) {
178.     sieve();
179.     cin >> n;
180.     n = sqrt(sqrt(n));
181.     for(int i = 1; i <= n; ++i) kq += check[i];
182.     cout << kq;
183. }
184.  
185. signed main (void) {
186.  BoostCompile();
187.  freopen("beaunum.inp", "r", stdin);
188.  freopen("beaunum.out", "w", stdout);
189.  Solution();
190.  return 0;
191. }
192.  
193. /* That's all about my code*/
194.  
195.