//Don't have to see. start------------------------------------------
var read = require('readline').createInterface({
	input: process.stdin, output: process.stdout
});
var obj; var inLine = [];
read.on('line', function(input){inLine.push(input);});
read.on('close', function(){
	obj = init(inLine);
	console.error('\n↑入力 ↓出力');
	Main();
});
function makeClone(obj){return (obj instanceof Set) ? new Set(Array.from(obj)) : JSON.parse(JSON.stringify(obj));}
function nextInt(){return myconv(next(),1);} function nextStrArray(){return myconv(next(),2);}
function nextIntArray(){return myconv(next(),4);} function nextCharArray(){return myconv(next(),6);}
function next(){return obj.next();} function hasNext(){return obj.hasNext();}
function init(input){  
	return {
		list : input, index : 0, max : input.length,
		hasNext : function(){return (this.index < this.max);},
		next : function(){if(this.hasNext()){return this.list[this.index++];}else{throw 'ArrayIndexOutOfBoundsException ‚There is no more input';}}
	};
}
function myout(s){console.log(s);}
function myerr(s){console.error('debug:' + require('util').inspect(s,false,null));}
//param "no" is
//unknown or outlier : return i. 1: parseInt.
//2: split space. 4: split space and parseInt.
//6: split 1 character. 7: split 1 character and parseInt.
//8: join space. 9: join nextline. 0: join no character.
function myconv(i,no){try{switch(no){case 1:return parseInt(i);case 2:return i.split(' ');case 4:return i.split(' ').map(Number);case 6:return i.split('');case 7:return i.split('').map(Number);case 8:return i.join(' ');case 9:return i.join('\n');case 0:return i.join('');default:return i;}}catch(e){return i;}}

//Don't have to see. end------------------------------------------
function Main(){
	var N = nextInt();
	var map = sieveOfEratos(N);
	myerr(map.size);
	var output = 0;
	var list = Array.from(map);
	for(var i = 0; i < list.length; i++){
		if(map.has(Math.sqrt(list[i] + 2))){
			output++;
		}
	}
	myout(Math.max(output * 2 - 1, 0));
}
function sieveOfEratos(val){
  var primes = new Set();
  var nums = new Set();
  var used = [2,3,5,7,11];//これらは既に素数であるとする
  var underPrime = 13;//この値から+2ごとに追加。↑の値で割り切れたものは何もしない
  if(val <= 1){
     return nums;
  }
  for(var i = 0; i < used.length; i++){if(used[i] <= val){nums.add(used[i]);}}
  for(var i = underPrime; i <= val; i = i + 2){
    var continued = false;
    for(var j = 0; j < used.length; j++){
      if(i % used[j] == 0){continued = true; break;}
    }
    if(continued){continue;}
    nums.add(i);
  }
  for(var i = 2; i <= Math.sqrt(val); (i == 2) ? i++ : i = i + 2){
    if(!nums.has(i)){continue;}
    var count = 1;
    while(i * count <= val){
      if(i <= 11 && used.indexOf(i) != -1){break;}
      if(count == 1){primes.add(i);}
      nums.delete(i * count);
      count++;
    }
  }
  var primeItr = Array.from(primes);
  for(var i = 0; i < primeItr.length; i++){
    nums.add(primeItr[i]);
  }
  return nums;
}