cf 714A

#include<stdio.h>

long long min(long long a, long long b)
{
    if(a < b) return a;
    else return b;
}

long long max(long long a, long long b)
{
    if(a > b) return a;
    else return b;
}

int main()
{
    long long l1, r1, l2, r2, k;
    scanf("%lld %lld %lld %lld %lld", &l1, &r1, &l2, &r2, &k);

    //long long ans = r1 - l2 + 1;
    if(min(r1, r2) < max(l1, l2)) printf("0\n");
    else if(max(l1, l2) <= k && k <= min(r1, r2)) printf("%lld\n", min(r1, r2) - max(l1, l2));
    else printf("%lld\n", min(r1, r2) - max(l1, l2) + 1);
}