#include <bits/stdc++.h>
using namespace std;
#define ull unsigned long long
#define ll long long
#define ld long double
#define pb push_back
#define f first
#define s second
#define sz(x) (int)x.size()
#define all(x) x.begin(),x.end()
#define pii pair<int,int>
#define pll pair<ll,ll>
#define pld pair<ld,ld>
#define pdd pair<double,double>
#define mp make_pair
#define AmirMakaM ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0)
// solve it
const ull SEED = chrono::steady_clock::now().time_since_epoch().count();
mt19937_64 mrand(SEED);
ull rnd(ull x = ~(0ull)) {return mrand() % x;}
const ll MOD = 998244353;
const ll INF = 1e16+20;
const int inf = 1e9 + 7;
const ll N = 5e5+5;
const ll M = 2e3+1;
const double pi = 2*acos(0.0);
const int dx[] = {1,-1,0,0}, dy[] = {0,0,1,-1};
int n;
pll a[N];
void solve() {
cin >> n;
for(int i=1; i<=n; i++) {
cin >> a[i].f >> a[i].s;
}
sort(a+1,a+n+1);
ll ans = 0;
for(int i=1; i<=n; i++) {
ll s = 0;
for(int j=i; j<=n; j++) {
s += a[j].s;
ans = max(ans,s-a[j].f+a[i].f);
}
}
cout << ans;
}
int main() {
AmirMakaM;
srand(SEED);
//freopen("walk.in", "r", stdin);
//freopen("walk.out", "w", stdout);
int ttt = 1;
//cin >> ttt;
while(ttt--) {
solve();
}
return 0;
}
