51Nod 1248 2 3 5 7 的倍数 容斥

#include<iostream>   
#include<algorithm>
#include<vector> 
#include<string.h>
#include<map>
using namespace std;
typedef long long ll;
const int MAX = 5e4 + 5;
ll n, t;
int main()
{
    cin >> n;
    ll a, b, c, d;
    a = n / 2 + n / 3 + n / 5 + n / 7;
    b = n / 6 + n / 10 + n / 14 + n / 15 + n / 21 + n / 35;
    c = n / 30 + n / 42 + n / 105+n/70;
    d = n / 210;
    cout << n - a + b - c + d << endl;
    return 0;
}