#include <iostream>
#include <fstream>
#include <vector>
#include <cstdlib>
#include <bits/stdc++.h> 
#include <cmath>  

using namespace std;

int n = 0;
vector<unsigned long long> v;

void Input()
{
    string line;
    string line2;
    ifstream myfile;
    	
	
    myfile.open("pairs.in");
    myfile >> n;
    for(int i = 0; i < n; i++)
    {
		getline ( myfile, line, ' ' );
		
        unsigned long long num = atoi( line.c_str());
		 
        v.push_back(num);
        
		getline ( myfile, line2, ' ' );
		
        unsigned long long num2 = atoi( line2.c_str());
		 
        v.push_back(num2);
    }
    
    myfile.close();
}

void Output(int minSum)
{
	ofstream myfile;
  	myfile.open ("pairs.out");
  	myfile << minSum<<endl;
  	myfile.close();
}

int main()
{	
	Input();
    sort(v.begin(), v.end());
    
    vector<unsigned long long>::iterator i; 
	for(i = v.begin(); i<v.end()-1; i++)
	{
     	if(*i == *(i+1))
     	{
        	v.erase(i);
         	v.erase(i);
          	i--;
     	} 
	}
	
    unsigned long long minSum = 0;
    
    for (int i = 0; i < v.size(); i+=2)
    {
        unsigned long long sum = abs (v.at(i+1) - v.at(i));
        
        minSum += sum;
    }
    
    Output(minSum);
    
    return 0;
}