#include <iostream>
#include <fstream>
using namespace std;
ifstream in("stergeri.in");
ofstream out("stergeri.out");
int main()
{
    int n,m,k;
    in>>n>>m>>k;
    int s=0;
    for(int i=1;i<=m;i++)
    {
        int a,b;
        in>>a>>b;
        if(b<k)
            s=s+b-a+1;
        if(a<k && b>k)
            s=s+b-k+1;
    }
    out<<s;
    return 0;
}