#include <iostream>
using namespace std;int main()
{long long a,b,c,d,k,left,right,sum = 0;cin >> a >> b >> c >> d >> k;if(a <= c && c <= b && b <= d){left = c;right = b;sum = b-c+1;}else if(a <= c && d <= b){left = c;right = d;sum = d-c+1;}else if(c <= a && a <= d && d <= b){left = a;right = d;sum = d-a+1;}else if(c <= a && b <= d){left = a;right = b;sum = b-a+1;}if(sum && left <= k && k <= right)  sum--;cout << sum << endl;return 0;
}