#define NDEBUG
#ifdef NDEBUG
#define dbg(TXTMSG) if constexpr (false) cerr << "lol"
#define dbgv(VARN) ((void)0)
#define dbgfor(COND) if constexpr (false) for (COND)
#else
#define _GLIBCXX_DEBUG 1
#define _GLIBCXX_DEBUG_PEDANTIC 1
#pragma GCC optimize("trapv")
#define dbg(TXTMSG) cerr << "\n" << TXTMSG
#define dbgv(VARN) cerr << "\n" << #VARN << " = "<< VARN << ", line: " << __LINE__ << "\n"
#define dbgfor(COND) for (COND)
#endif
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pll = pair<ll,ll>;
#define e0 first
#define e1 second
constexpr ll INFTY = 2e18;
ll N;
int main() {
cin >> N;
vector<pll> SV(N);
for (ll i = 0; i < N; ++i)
{
cin >> SV[i].e0 >> SV[i].e1;
}
sort(SV.begin(),SV.end());
vector<ll> dp(N);
dp[0] = SV[0].e1;
for (ll i = 1; i < N; ++i)
{
dp[i] = max(SV[i].e1, dp[i-1] - SV[i].e0 + SV[i-1].e0 + SV[i].e1);
}
ll outp = 0;
for (ll i : dp)
{
dbg(i);
outp = max(outp,i);
}
cout << outp;
}
