#include <iostream>
using namespace std;

const int SIZE = 100;
int main(){
    int p[SIZE];
    int n, tot, i, cn;
    tot = 0;
    cin >> n;
    for(i = 1; i <= n; i++)
        p[i] = 1;
    for(i = 2; i <= n; i++){
        if(p[i] == 1)
            tot++;
        cn = i * 2;
        while(cn <= n){
   			p[cn] = 0;
            cn += i;
        }
    }
    cout << tot << endl;

    return 0;
}

请填写答案。

{{ input(1) }}