#include <bits/stdc++.h>

using namespace std;
long long m, n, k, q;
int main() {
    cin >> m >> n >> k >> q;
    if (m >= k && n >= k) {
        cout << m + n - k + q;
    }
    else cout << "NONE";
    return 0;
}

\begin{array}{}\color{#473992}{l}\color{#2D2F92}{e}\color{#006795}{d}\color{Violet}{u}\color{#3FBC9D}{c}\color{#A4D3EE}{t}\color{#00AEB3}{r}\color{#00B4CE}{u}\color{#00B4CE}{n}\color{#46C5DD}{g}\color{#007ACC}{a}\color{#00B0F0}{n}\color{#7977B8}{h}\end{array}