#include<stdio.h>
long n,m,k,a,b,i;
int main()
{
	freopen("stergeri.out","w",stdout);
	freopen("stergeri.in","r",stdin);
	scanf("%ld %ld %ld",&n,&m,&k);
	for (i=1;i<=m;i++)
	{
		scanf("%ld%ld",&a,&b);
		k+=(b-a+1);
	}
	printf("%ld",k);
}