#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
#define MASK(i) (1LL << (i))
#define GETBIT(mask, i) (((mask) >> (i)) & 1)
#define ALL(v) (v).begin(), (v).end()
ll max(ll a, ll b){return (a > b) ? a : b;}
ll min(ll a, ll b){return (a < b) ? a : b;}
ll gcd(ll a, ll b){
while(a > 0 && b > 0){
if (a > b) a %= b;
else b %= a;
}
return a + b;
}
ll LASTBIT(ll mask){return (mask) & (-mask);}
int pop_cnt(ll mask){return __builtin_popcountll(mask);}
int ctz(ll mask){return __builtin_ctzll(mask);}
int logOf(ll mask){return __lg(mask);}
mt19937_64 rng(chrono::high_resolution_clock::now().time_since_epoch().count());
ll rngesus(ll l, ll r){return l + (ull) rng() % (r - l + 1);}
template <class T1, class T2>
bool maximize(T1 &a, T2 b){
if (a < b) {a = b; return true;}
return false;
}
template <class T1, class T2>
bool minimize(T1 &a, T2 b){
if (a > b) {a = b; return true;}
return false;
}
template <class T>
void printArr(T& container, string separator = " ", string finish = "\n"){
for(auto item: container) cout << item << separator;
cout << finish;
}
template <class T>
void remove_dup(vector<T> &a){
sort(ALL(a));
a.resize(unique(ALL(a)) - a.begin());
}
void solve(){
int n; cin >> n;
vector<pair<int, int>> a(n);
for(int i = 0; i< n; ++i) cin >> a[i].first >> a[i].second;
for(int i = 0; i< n; ++i) {
a[i] = {a[i].first + a[i].second, a[i].second - a[i].first};
}
sort(ALL(a));
map<int, int> mp;
for(pair<int, int> i: a) {
mp[i.first] = i.second;
}
a = vector<pair<int,int>> (ALL(mp));
reverse(ALL(a));
int ans = 0, ma = -2e9;
for(pair<int, int> i: a){
ans += maximize(ma, i.second);
}
cout << ans << "\n";
}
int main(void){
ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
clock_t start = clock();
solve();
cerr << "Time elapsed: " << clock() - start << "ms!\n";
return 0;
}
