Стратегия контрольная

//
//  main.cpp
//  STRATEGY
//
//  Created by Андрей Москалёв on 17.01.17.
//  Copyright © 2017 Андрей Москалёв. All rights reserved.
//

#include <iostream>
#include <vector>

using namespace std;

int main(int argc, const char * argv[]) {
    int a_from, a_to, b_from, b_to, cnt = 0;
    cin >> a_from >> a_to >> b_from >> b_to;
    int minimum = min(min(a_from, a_to), min(b_from, b_to));
    int maximum = max(max(a_from, a_to), max(b_from, b_to));
    vector <int> a(maximum + 1, 0);
    for (int i = min(a_from, a_to); i <= max(a_from, a_to); ++i) ++a[i];
    for (int i = min(b_from, b_to); i <= max(b_from, b_to); ++i) ++a[i];
    for (int i = minimum; i <= maximum; ++i) {
        if (a[i] > 1) ++cnt;
    }
    cout << cnt;
}