#include<bits/stdc++.h>
#define F first
#define S second
#define MP make_pair
#define pb push_back
#define endl '\n'

using namespace std;

typedef long long LL;
typedef pair< int, int > P;
typedef pair< LL, LL > LP;
typedef pair< int, P > iP;
typedef pair< P, P > PP;

static const int INF = INT_MAX;
static const LL LINF = LLONG_MAX;
static const int MIN = INT_MIN;
static const LL LMIN = LLONG_MIN;
static const int MOD = 1000000007;
static const int SIZE = 500005;

int dx[] = {0, -1, 1, 0};
int dy[] = {-1, 0, 0, 1};

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    
    LL n;
    cin >> n;
    LL res = 0;
    int prime[SIZE] = {};
    for( LL i = 2; i <= 500000; ++i ) {
        if( !prime[i] ) {
            for( LL j = i + i; j <= 500000; j += i ) prime[j] = 1;

        }
    }
    vector< int > v;
    for( int i = 2; i <= n; ++i ) {
        if( !prime[i] ) v.pb( i );

    }

    for( int i = 0; i < v.size(); ++i ) {
        double r = sqrt( 2 + v[i] );
        int tmp = r;
        if( r - tmp == 0 ) {
            if( !prime[tmp] ) res += 2;
        
        }
    }
    cout << res - 1 << endl;
    return 0;
}