#include <bits/stdc++.h>
#define fi first
#define se second
#define pb push_back
using namespace std;
typedef long long ll;
typedef double dbl;
typedef pair<ll,ll> pii;
const int maxn = 5e5+5,MOD = 1e9+7;
ll N,dp[maxn],ans;
pii A[maxn];
int main(){
ios::sync_with_stdio(false);
cin.tie(NULL);
cin >> N;
for(int i =1; i <= N; i++) cin >> A[i].fi >> A[i].se;
sort(A+1,A+N+1);
for(int i =1; i <= N; i++){
dp[i] = max(0LL,dp[i-1] - (A[i].fi-A[i-1].fi))+A[i].se;
ans = max(ans,dp[i]);
}
cout << ans << '\n';
}
