// Author: JustKitkat
// Status: WIP
#include <bits/stdc++.h>
// #include <ext/pb_ds/assoc_container.hpp>
// #include <ext/pb_ds/tree_policy.hpp>
using namespace std;
// #pragma GCC optimize("O3,unroll-loops")
// #pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
#define int long long
#define el "\n"
#define arr array
#define ll long long
#define ld long double
#define ii pair<int, int>
#define pll pair<long long, long long>
#define vi vector<int>
#define vll vector<long long>
#define vii vector<ii>
#define vllll vector<pll>
#define umap unordered_map
#define uset unordered_set
#define pb push_back
#define mp make_pair
#define F first
#define S second
#define all(a) (a).begin(), (a).end()
#define FOR(a,b) for(int i=a;i<b;++i)
#define DFOR(a,b) for(int i=a;i>=b;--i)
#define JFOR(a,b) for(int j=a;j<b;++j)
#define DJFOR(a,b) for(int j=a;j>=b;--j)
#define show(x) cerr << #x << " is " << x << endl;
#define show2(x,y) cerr << #x << " is " << x << " " << #y << " is " << y << endl;
#define show3(x,y,z) cerr << #x << " is " << x << " " << #y << " is " << y << " " << #z << " is " << z << endl;
#define show_vec(a) { for(auto &x:a)cerr<<x<<' '; cerr<<endl; }
#define discretize(x) sort(x.begin(), x.end()); x.erase(unique(x.begin(), x.end()), x.end());
void dbg_out() { cerr << endl; }
template<typename Head, typename... Tail> void dbg_out(Head H, Tail... T) { cerr << ' ' << H; dbg_out(T...); }
#define dbg(...) cerr << "(" << #__VA_ARGS__ << "):", dbg_out(__VA_ARGS__)
string to_upper(string a) { for (int i=0;i<(int)a.size();++i) if (a[i]>='a' && a[i]<='z') a[i]-='a'-'A'; return a; }
string to_lower(string a) { for (int i=0;i<(int)a.size();++i) if (a[i]>='A' && a[i]<='Z') a[i]+='a'-'A'; return a; }
bool prime(ll a) { if (a==1) return 0; for (int i=2;i<=round(sqrt(a));++i) if (a%i==0) return 0; return 1; }
void yes() { cout<<"YES\n"; }
void no() { cout<<"NO\n"; }
mt19937_64 rnd(chrono::steady_clock::now().time_since_epoch().count());
#define __time__ { auto duration = chrono::duration<double>( /* Show runtime */ \
chrono::high_resolution_clock::now() - BEG); cout<<"Time: "<<duration.count()<<endl;}
// PBDS -> initialise using `ordered_set s;` -> change to greater<int> for reversed order.
// using namespace __gnu_pbds;
// #define ordered_set tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update>
// #define ordered_multiset tree<int, null_type, less_equal<int>, rb_tree_tag, tree_order_statistics_node_update>
const int MAX_N = 1e5 + 5;
const ll INF = 1e15;
const ll MOD = 1e9+7;
const double PI = acos(-1);
const auto BEG = std::chrono::high_resolution_clock::now(); //Begining of the program
ll n=0, m=0, k=0, q=0;
void solve(int tc){
cin>>n;
map<int,int>mm;
FOR(0,n){
int x,y;
cin>>x>>y;
mm[x]+=y;
}
vii a;
for(auto &x:mm)a.pb(x);
int ans=a[0].S;
int cur=a[0].S;
FOR(0,a.size()-1){
cur=max(a[i+1].S,cur-(a[i+1].F-a[i].F)+a[i+1].S);
ans=max(ans,cur);
}
cout<<ans;
}
signed main(){
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
// freopen("out", "w", stdout);
// freopen("in", "r", stdin);
int tc = 1;
// cin >> tc;
for (int t = 1; t <= tc; t++) {
// cout << "Case #" << t << ": ";
solve(t);
}
//__time__ //Runtime
}
