#include <iostream>
#include <fstream>

using namespace std;
int n,m,k;
struct
{
    int x,y;
}a[100004];


int main()
{
    int i;
    ifstream fin("stergeri.in");
    fin>>n>>m>>k;
    for(i=1;i<=m;i++)
        fin>>a[i].x>>a[i].y;
    fin.close();


    for(i=m;i>=1;i--)
        k=k+a[i].y-a[i].x+1;

    ofstream fout("stergeri.out");
    fout<<k;
    fout.close();


    return 0;
}