#include <bits/stdc++.h>
    using namespace std;
    typedef long long ll;
    typedef long double ld;

    int a, b, c, d;

    int main() {

        ios_base::sync_with_stdio(0);
        cin.tie(0);
        cout.tie(0);
    #ifdef _DEBUG
        freopen("input.txt", "r", stdin);
        freopen("output.txt", "w", stdout);
    #endif

        cin >> a >> b >> c >> d;
        int res = 0;
        for (int i = 1; i * i <= b; ++i) {
            int l1 = (a - 1) / i + 1, r1 = b / i;
            int l2 = (c - 2 * i - 1) / 2 + 1 , r2 = (d - 2 * i) / 2;
            if (r2 < i || r1 < i) {
                continue;
            }
            l1 = max(l1, i);
            l2 = max(l2, i);
            if ((l1 <= l2 && l2 <= r1) || (l2 <= l1 && l1 <= r2)) {
                res += min(abs(r1 - l2) + 1, abs(r2 - l1) + 1);
            }
        }
        cout << res << "\n";

        return 0;
    }