148A - Insomnia cure

#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <iostream>
#include <string>
#include <algorithm>
using namespace std;

int gcd(int a, int b) {
    return b == 0 ? a : gcd(b, a % b);
}

int lcm(int a, int b) {
    return a / gcd(a, b) * b;
}

int main() {

    int a[4], d;
    int ans = 0;
    cin >> a[0] >> a[1] >> a[2] >> a[3] >> d;
    for(int i = 1; i < 16; ++i) {
        int x = 1, cnt = 0;
        for(int j = 0; j < 4; ++j) {
            if(i&(1<<j)) {
                x = lcm(x, a[j]);
                cnt++;
            }
        }
        if(cnt&1) {
            ans += d / x;
        } else {
            ans -= d / x;
        }
    }
    cout << ans << endl;
    return 0;
}