#include<bits/stdc++.h>
#include<ext/pb_ds/assoc_container.hpp>
/**zagaro & lauren <3**/
#define mod 1000000007 //1e9 + 7
#define pi acos(-1)
#define wl while
#define str string
#define ENDL "\n"
#define sal ' '
#define tp_set ll
#define prc(n) cout.precision(n);cout<<fixed;
#define ord_set tree<tp_set, null_type, less<tp_set>, rb_tree_tag, tree_order_statistics_node_update>
typedef long long ll;
typedef bool bl;
typedef char car;
using namespace std;
using namespace __gnu_pbds;
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
ll n, r, a;
r=a=0;
cin>>n;
vector<pair<ll,ll> > vec(n+1);
for(int i=1;i<=n;i++)cin>>vec[i].first>>vec[i].second;
sort(vec.begin(), vec.end());
vec[0].first = vec[1].first;
for(int i=1;i<=n;i++){
a += vec[i].second-(vec[i].first-vec[i-1].first);
if(a <= 0)a = vec[i].second;
r = max(r, a);
}
cout<<r<<ENDL;
return 0;
}
