#include<bits/stdc++.h>
using namespace std;
bool asd(int x){
	for(int i=2;i<=sqrt(x);i++){
		if(x%i==0){
			return true;
		}
	}
	return false;
}
int main(){
	int a,b,c=0;
	cin>>a;
	for(int i=4;i<=a;i++){
		if(asd(i)){
			b++;
			if(b>c){
				c=b;
			}
		}else{
			b=0;
		}
	}
	cout<<c;
}
/**************************************************************
	Problem: 1587
	User: zhengzihao
	Language: C++
	Result: Wrong Answer
****************************************************************/