#include<stdio.h>
using namespace std;

 int main()
 { long long n,m,k,i,x,y;
	 
	 FILE *f = fopen("stergeri.in", "r");
	 FILE *g = fopen("stergeri.out", "w");
	
	 fscanf(f, "%lld%lld%lld", &n, &m, &k);
	 
	 for(i = 1; i <= m; i ++)
		 {
			 fscanf(f, "%lld%lld", &x, &y);
			 k += (y - x + 1);
		 }
	 
	 fprintf(g, "%lld\n", k);
	 
	 fclose(f);
	 fclose(g);
	 return 0;
 }