#include <iostream>
#include <fstream>
#include <cmath>
using namespace std;
ifstream in("heavymetal.in");
ofstream out("heavymetal.out");
int main(){
	int n, i, v[100001], u[100001], p[100001], j;
	in>>n;
	for(i=1; i<=n; i++){
        in>>v[i]>>u[i];
	}
	for(i=1; i<=n; i++){
        if(p[i]!=1){
            for(j=1; j<=n; j++){
                if(i!=j&&((v[j]>v[i]&&v[j]<u[i])||(u[j]>v[i]&&u[j]<u[i]))){
                    if(abs(v[j]-u[j])>abs(v[i]-u[i])){
                        p[i]=1;
                    }else{
                        p[j]=1;
                    }
                }
            }
        }
	}
	int s=0;
	for(i=1; i<=n; i++){
        if(p[i]!=1){
            s+=abs(v[i]-u[i]);
        }
	}
	out<<s;
	return 0;
}