#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;
	   if(x2>x1)
	      s-=(x2-x1)+1;
	   else
	      s-=(x1-x2)+1;
	}
  s-=k;
  g<<n-s;
  return 0;
  }