#include <bits/stdc++.h>
using namespace std;

bool prime[50000005];
int tmp[50000005],sum[50000005];

int main() {
    int N;
    cin >> N;
    memset(prime,true,sizeof(prime));
    prime[0] = false;
    prime[1] = false;
    for(int i = 2; i <= 50000000; i++) {
        if(!prime[i]) {
            continue;
        }
        for(int j = i*2; j <= 50000000; j += i) {
            prime[j] = false;
        }
    }
    for(int i = 1; i <= 50000000; i++) {
        tmp[i] = i;
    }
    for(int i = 2; i*i <= 50000000; i++) {
        if(!prime[i]) {
            continue;
        }
        for(int j = i*i; j <= 50000000; j += i*i) {
            while (tmp[j]%(i*i) == 0) {
                tmp[j] /= i*i;
            }
        }
    }
    for(int i = 1; i*i <= 50000000; i++) {
        sum[i*i]++;
    }
    for(int i = 1; i <= 50000000; i++) {
        sum[i+1] += sum[i];
    }
    int ans = 0;
    for(int i = 1; i <= N; i++) {
        ans += sum[N/tmp[i]];
    }
    cout << ans << endl;
}