B

#include <bits/stdc++.h>
using namespace std;

int main() {
    long long l1, r1, l2, r2, k;
    cin >> l1 >> r1 >> l2 >> r2 >> k;
    long long l = max(l1, l2);
    long long r = min(r1, r2);
    long long ans = max(0LL, r - l + 1);
    if (l <= k && k <= r)
        ans--;
    cout << ans << endl;
}