#include <fstream>
#include <algorithm>
#define nmax 100005

using namespace std;

int n, dp[nmax][3];
pair<int,int> v[nmax];

ifstream f("heavymetal.in");
ofstream g("heavymetal.out");

void citeste(){

    f >> n;

    for(int i=1; i<=n; i++){
        int x,y;
        f >> x >> y;
        v[i]=(make_pair(y-x, x));
    }

    sort(v+1, v+n+1);

}

void rezolva(){

    for(int i=1; i<=n; i++){
        int val = v[i].first;//am durata concertului
        int start = v[i].second;;
        int final = val + start;
        dp[i][0] = val;
        dp[i][1] = final;
        int Max = 0, y = final;
        for(int j=1; j<i; j++){
            if (start >= dp[j][1]){//daca pot continua un concert
                Max = max(Max, dp[j][0]);
                int y = dp[j][1];
            }
        }
        dp[i][0] = Max+val;
        dp[i][1] = y;
    }

    g << dp[n][0] << "\n";

}

int main(){

    citeste();
    rezolva();

    f.close();
    g.close();

    return 0;

}