#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); i++)
#define REP(i,a,b) for(int i=(a);i<(b);i++)
#define all(v) begin(v),end(v)
#define fi first
#define se second
template<typename A, typename B> inline bool chmax(A &a, B b) { if (a<b) { a=b; return 1; } return 0; }
template<typename A, typename B> inline bool chmin(A &a, B b) { if (a>b) { a=b; return 1; } return 0; }
using ll = long long;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
constexpr ll inf = 2e9;
constexpr ll llinf = 9e18;
//constexpr ll MOD = 998244353;
constexpr ll MOD = 1000000007;
const double pai=acos(-1);

int main() {
    //cout<<fixed<<setprecision(15);
    int n;cin>>n;
    vector<ll> p(n),a(n);
    rep(i,n)cin>>p[i]>>a[i];
    vector<ll> dp(n+1);
    rep(i,n){
        if(i+1<n)chmax(dp[i+1],dp[i]+a[i]+p[i+1]);
        chmax(dp[i+1],dp[i]+p[i]);
    }
    cout<<dp[n]<<endl;
}