#include <bits/stdc++.h>
using namespace std;
int main()
{
   int n;
   scanf("%d",&n);
   int PS[n]={0};
   int CY[n]={0};
   int diff[n][2]={0};
   for(int i=0;i<n;i++)
   {
       diff[i][0]=i;
   }
   for(int i=0;i<n;i++)
   {
       scanf("%d",&PS[i]);
       scanf("%d",&CY[i]);
       diff[i][1]=PS[i]-CY[i];
   }
   for(int mask=1;mask<n;mask++)
   {
       for(int i=0;i<n-1;i++)
       {
           if(diff[i][1]>diff[i+1][1])
           {
               int temp=diff[i][1];
               diff[i][1]=diff[i+1][1];
               diff[i+1][1]=temp;
               temp=diff[i][0];
               diff[i][0]=diff[i+1][0];
               diff[i+1][0]=temp;
           }
       }
   }
   int res=0;
   for(int i=0;i<n/2;i++)
   {
       res+=CY[diff[i][0]];
   }
   for(int i=n/2;i<n;i++)
   {
       res+=PS[diff[i][0]];
   }
   printf("%d\n",res);

}