#include<stdio.h>
long n,i,a,b,min,max;
int main()
{
freopen("heavymetal.in","r",stdin);
freopen("heavymetal.out","w",stdout);
scanf("%ld",&n);
scanf("%ld%ld",&a,&b);
min=a;max=b;
for(i=2;i<=n;i++)
	{
	scanf("%ld%ld",&a,&b);
	if(a<min)
		min=a;
	if(b>max)
		max=b;
	}
printf("%ld",max-min);
return 0;
}