#include<fstream>
using namespace std;
ifstream f("stergeri.in");
ofstream g("stergeri.out");
int n,m,k,i,a[100001],b[100001];
int main()
{	f>>n>>m>>k;
	for(i=1;i<=m;++i) f>>a[i]>>b[i];
	for(i=m;i>=1;--i) k=k+b[i]-a[i]+1;
	g<<k<<"\n"; g.close(); return 0;
}