#include <stdio.h>
#include <iostream>
#include <math.h>

using namespace std;

int main() {
	int n;

	while (cin >> n) {
		int counter = 1;
		
		if(n < 1000){
			for (int i = 3; i <= n; i=i+2) {
				int kari = 1;
				for (int j = 3; j < i; j=j+2) {
					kari = i % j;
					if(kari == 0) {
						break;
					}
				} if (kari != 0) {
					counter++;
				}
			}
		}else if(n < 10000){
			counter = 168;
			for (int i = 1001; i <= n; i=i+2) {
				int kari = 1;
				for (int j = 3; j < i; j=j+2) {
					kari = i % j;
					if(kari == 0) {
						break;
					}
				} if (kari != 0) {
					counter++;
				}
			}
		} else if(n < 100000){
			counter = 1229;
			for (int i = 10001; i <= n; i=i+2) {
				int kari = 1;
				for (int j = 3; j < i; j=j+2) {
					kari = i % j;
					if(kari == 0) {
						break;
					}
				} if (kari != 0) {
					counter++;
				}
			}
		} else if(n < 200000){
			counter = 9592;
			for (int i = 100001; i <= n; i=i+2) {
				int kari = 1;
				for (int j = 3; j < i; j=j+2) {
					kari = i % j;
					if(kari == 0) {
						break;
					}
				} if (kari != 0) {
					counter++;
				}
			}
		} else if(n < 300000){
			counter = 17984;
			for (int i = 200001; i <= n; i=i+2) {
				int kari = 1;
				for (int j = 3; j < i; j=j+2) {
					kari = i % j;
					if(kari == 0) {
						break;
					}
				} if (kari != 0) {
					counter++;
				}
			}
		} else if(n < 400000){
			counter = 25997;
			for (int i = 300001; i <= n; i=i+2) {
				int kari = 1;
				for (int j = 3; j < i; j=j+2) {
					kari = i % j;
					if(kari == 0) {
						break;
					}
				} if (kari != 0) {
					counter++;
				}
			}
		} else if(n < 500000){
			counter = 33860;
			for (int i = 400001; i <= n; i=i+2) {
				int kari = 1;
				for (int j = 3; j < i; j=j+2) {
					kari = i % j;
					if(kari == 0) {
						break;
					}
				} if (kari != 0) {
					counter++;
				}
			}
		} else if(n < 600000){
			counter = 41538;
			for (int i = 500001; i <= n; i=i+2) {
				int kari = 1;
				for (int j = 3; j < i; j=j+2) {
					kari = i % j;
					if(kari == 0) {
						break;
					}
				} if (kari != 0) {
					counter++;
				}
			}
		} else if(n < 700000){
			counter = 49098;
			for (int i = 600001; i <= n; i=i+2) {
				int kari = 1;
				for (int j = 3; j < i; j=j+2) {
					kari = i % j;
					if(kari == 0) {
						break;
					}
				} if (kari != 0) {
					counter++;
				}
			}
		} else if(n < 800000){
			counter = 56543;
			for (int i = 700001; i <= n; i=i+2) {
				int kari = 1;
				for (int j = 3; j < i; j=j+2) {
					kari = i % j;
					if(kari == 0) {
						break;
					}
				} if (kari != 0) {
					counter++;
				}
			}
		} else if(n < 900000){
			counter = 63951;
			for (int i = 800001; i <= n; i=i+2) {
				int kari = 1;
				for (int j = 3; j < i; j=j+2) {
					kari = i % j;
					if(kari == 0) {
						break;
					}
				} if (kari != 0) {
					counter++;
				}
			}
		} else if (n < 999999){
			counter = 71274;
			for (int i = 900001; i <= n; i=i+2) {
				int kari = 1;
				for (int j = 3; j < i; j=j+2) {
					kari = i % j;
					if(kari == 0) {
						break;
					}
				} if (kari != 0) {
					counter++;
				}
			}
		} else {
			counter = 78498;
		}
		cout << counter << endl;
	}

	return 0;
}