#include <fstream>

using namespace std;

ifstream in("stergeri.in");
ofstream out("stergeri.out");

int n,m,k;

int main()
{
    int i,x,y;
    in>>n>>m>>k;
    for(i=1;i<=m;i++)
    {
        in>>x>>y;
        k+=(y-x+1);
    }
    out<<k;
    in.close();
    out.close();
    return 0;
}