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;}