#include <stdio.h>
#include <stdbool.h>
typedef long long ll;

bool is_prime[500005];
ll list_prime[500005];

ll calc_prime(ll n);

int main()
{
    ll n;
    ll m;
    ll ans = 0;
    
    scanf("%lld", &n);

    m = calc_prime(n);

    for (ll i = 0; i < m; i++) {
        for (ll j = i; j < m; j++) {
            ll p = list_prime[i];
            ll r = list_prime[j];

            ll q = r * r - p;

            if (q >= 0 && q <= n && is_prime[q]) {
                if (i == j) {
                    ans++;
                }
                else {
                    ans += 2;
                }
            }
        }
    }

    printf("%lld\n", ans);

    return 0;
}

ll calc_prime(ll n)
{
    ll cnt = 0;
    
    for (ll i = 2; i <= n; i++) {
        is_prime[i] = true;
    }

    for (ll i = 2; i <= n; i++) {
        if (is_prime[i]) {
            list_prime[cnt] = i;
            cnt++;
            
            for (ll j = i + i; j <= n; j += i) {
                is_prime[j] = false;
            }
        }
    }

    return cnt;
}