codeforces/codeforces/26/A.cpp at main · ychaaibi/codeforces · GitHub

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//__________Includes__________________//

# include               <iostream>
# include               <algorithm>
# include               <vector>
# include               <string>
# include               <map>
# include               <unordered_map>
# include               <set>
# include               <unordered_set>
# include               <bitset>
# include               <queue>
# include               <stack>
# include               <complex>
# include               <cmath>
# include               <climits>
# include               <cstring>

//____________Containers_Define__________//

# define    vi          vector<int>
# define    vll         vector<long long>
# define    vull        vector<unsigned long long>
# define    vvi         vector<vector<int> >
# define    vvll        vector<vector<long long> >
# define    vvull       vector<vector<unsigned long long> >
# define    vs          vector<string>
# define    vvs         vector<vector<string> >
# define    pii         pair<int, int>
# define    pis         pair<int, string>
# define    psi         pair<string, int>
# define    mpii        map<int, int>
# define    mpis        map<int, string>
# define    mpsi        map<string, int>
# define    mpiv        map<int, vector<int> >
# define    umpii       unordered_map<int, int>
# define    umpis       unordered_map<int, string>
# define    umpsi       unordered_map<string, int>
# define    umpiv       unordered_map<int, vector<int> >

//_____________Data_type________________//

# define    ll          long long
# define    ull         unsigned long long
# define    string      str

//_____________Methods__________________//

# define    mp          make_pair
# define    pb          push_back
# define    pf          push_front
# define    f           first
# define    s           second

using namespace std;

//______________Functions________________//

bool    isInt(double d)
{
    return ((double)(int)d - d == (double)0.00);
}

ull     fact(ull n)
{
    ull res = 1;

    while (n--) res *= (n + 1);
    return (res);
}

ull     C(ull n, ull k)
{
    vull    dpp(n + 1);
    vvull   dp(k + 1, dpp);

    for (int i=1; i<=n; i++) dp[1][i] = i;
    for (int i=2; i<=k; i++)
    {
        for (int j=1; j<=n; j++)
        {
            if (i > j)
                dp[i][j] = 0;
            else
                dp[i][j] = dp[i - 1][j - 1] + dp[i][j - 1];
        }
    }
    return (dp[k][n]);
}

bool    is_prime(long long nbr)
{
    long long    _sq = sqrtl(nbr);

    if (nbr == 2)
        return (true);
    if (nbr < 2 || (!(nbr % 2)))
        return (false);
    for (long long i = 3; i <= _sq; i += 2)
        if (!(nbr % i))
            return (false);
    return (true);
}

void    solve()
{
    int n;
    ull count = 0;
    cin >> n;
    for (int i=1; i<=n; i++)
    {
        int c = 0;
        for (int j=2; j<=(int)(i / 2); j++)
        {
            if (is_prime(j))
                c += !(i % j);
        }
        count += (c == 2);
    }
    cout << count << endl;
}

int main()
{
    int cases = 1;

    //cin >> cases;
    while (cases--)
        solve();
    return (0);
}