#include <bits/stdc++.h>
using namespace std;
#define FOR(i, j, k) for(int i=(j); i<=(k); i++)
#define FFOR(i, j, k) for(int i=(j); i<(k); i++)
#define DFOR(i, j, k) for(int i=(j); i>=(k); i--)
#define bug(x) cerr<<#x<<" = "<<(x)<<'\n'
#define pb push_back
#define mp make_pair
#define bit(s, i) (((s)>>(i))&1LL)
#define mask(i) ((1LL<<(i)))
#define builtin_popcount __builtin_popcountll
#define __builtin_popcount __builtin_popcountll
using ll=long long; using ld=long double;
mt19937_64 rng(chrono::high_resolution_clock::now().time_since_epoch().count()); const ld pi=acos(0)*2;
template <typename T> inline void read(T &x){char c; bool nega=0; while((!isdigit(c=getchar()))&&(c!='-')); if(c=='-'){nega=1; c=getchar();} x=c-48; while(isdigit(c=getchar())) x=x*10+c-48; if(nega) x=-x;}
template <typename T> inline void writep(T x){if(x>9) writep(x/10); putchar(x%10+48);}
template <typename T> inline void write(T x){if(x<0){ putchar('-'); x=-x;} writep(x);}
template <typename T> inline void writeln(T x){write(x); putchar('\n');}
#define taskname "Art"
int n;
class art{
public:
ll a, b;
void input(){
read(a);
read(b);
}
};
vector <art> v;
int main(){
#ifdef Aria
if(fopen(taskname".in", "r"))
freopen(taskname".in", "r", stdin);
#endif // Aria
read(n);
v.resize(n);
for(auto &x: v) x.input();
sort(v.begin(), v.end(), [](art A, art B){
return A.a<B.a;
});
ll m=-1e18;
ll ans=-1e18;
ll sum=0;
///start from i to j
///(sum[j]-sum[i-1])-(a[j]-a[i])
///(sum[j]-a[j])+(a[i]-sum[i-1])
for(auto x: v){
ans=max(ans, (sum+x.b)-x.a+m);
ans=max(ans, x.b);
m=max(m, x.a-sum);
sum+=x.b;
}
writeln(ans);
}
