#include <cstdio>
#include <fstream>

using namespace std;

int main ()
{
	int n,m,k;
	ifstream in ("stergeri.in");
	in>>n>>m>>k;
	for(int x,y;m;--m)
	{
		in>>x>>y;
		k+=y-x+1;
	}
	freopen ("stergeri.out","w",stdout);
	printf("%d",k);
	return 0;
}