#include<fstream>
using namespace std;
ifstream fin("stergeri.in");
ofstream fout("stergeri.out");
struct in
{
	int st,dr;
};
in a[100100];
int main()
{
	int n, m, k, i;
	fin >> n >> m >> k;
	for ( i = 1; i <= m; i++ )
		fin >> a[i].st >> a[i].dr;
	for ( i = m; i >= 1; i-- )
	{
		k += a[i].dr-a[i].st + 1;
	}
	fout << k;
	fin.close();
	fout.close();
	return 0;
}