#include<fstream.h>

int main()
{ unsigned long n,m,k,i,x1,x2,s;
  ifstream f("stergeri.in");
  ofstream g("stergeri.out");
  f>>n>>m>>k;s=n;
  for(i=1;i<=m;i++)
	  {f>>x1>>x2;
	   s-=(x2-x1)+1;}
  s-=k;s=n-s;
  g<<s;
  return 0;
  }