#include <iostream>
#include <math.h>
#include <vector>
#include <string>
#include <algorithm>
#include <queue>
#include <stack>
#include <map>
#include <cstring>
#include <iomanip>
#include <set>
#include <bitset>
using namespace std;
using ll = long long;
using pii = pair<int,int>;
using piii = tuple<int,int,int>;
#define endl '\n'
#define f first
#define s second
int main(){
int n;cin >> n;
vector<pii> vc = {{0,0}};
for(int i{};i < n;i++){
int a,b;cin >> a >> b;
vc.emplace_back(a,b);
}
sort(vc.begin(),vc.end());
int cur = 0;
int ans = 0;
for(int i{1};i <= n;i++){
cur = max(0,cur+vc[i-1].f-vc[i].f)+vc[i].s;
ans = max(ans,cur);
}
cout << ans;
}
