#include <iostream>

using namespace std;

int main()

{

    long long a,b,c,d,k,left,right,sum = ;

    cin >> a >> b >> c >> d >> k;

    if(a <= c && c <= b && b <= d)

    {

        left = c;

        right = b;

        sum = b-c+;

    }

    else if(a <= c && d <= b)

    {

        left = c;

        right = d;

        sum = d-c+;

    }

    else if(c <= a && a <= d && d <= b)

    {

        left = a;

        right = d;

        sum = d-a+;

    }

    else if(c <= a && b <= d)

    {

        left = a;

        right = b;

        sum = b-a+;

    }

    if(sum && left <= k && k <= right)  sum--;

    cout << sum << endl;

    return ;

}