int main(void)
{
   int M, L;
   int i, initial, end, l=0, n=0;
   int road[10000];         

   for (i=0; i<=L; ++i)
       road[i] = 1;

   for (i=0; i<M; ++i)
   {
       scanf("%d %d", &initial, &end);
	   for (l=initial; l<=end; ++l)
	       road[l] = 0;
   }

   for (i=0; i<=L; ++i)
   {
       if (road[i] == 1)
		   ++n;
   }
   
   printf("n = %d\n", n);

   return 0;
}