# include<iostream> using namespace std; bool isprime(int x){ if(x<=2||x%2==0) return 0; for(int i=2;i*i<=x;i++){ if(x%i==0) return 0; } return 1; } int main(){ int n,sum=0,temp=0; cin>>n; for(int i=2;i<=n;i++){ while(i>10){ temp=i; if(isprime(temp)==1) break; else temp=temp/10; } if(isprime(temp)==1) sum++; } cout<<sum; return 0; }