#include<bits/stdc++.h>
using namespace std;

typedef long long ll;
typedef pair<int,int> P;

#define p_ary(ary,a,b) do { cout << "["; for (int count = (a);count < (b);++count) cout << ary[count] << ((b)-1 == count ? "" : ", "); cout << "]\n"; } while(0)
#define p_map(map,it) do {cout << "{";for (auto (it) = map.begin();;++(it)) {if ((it) == map.end()) {cout << "}\n";break;}else cout << "" << (it)->first << "=>" << (it)->second << ", ";}}while(0)

template<typename T1,typename T2>ostream& operator<<(ostream& os,const pair<T1,T2>& a) {os << "(" << a.first << ", " << a.second << ")";return os;}

int main() {
    int n;
    cin >> n;
    vector<int> a(n*2);
    vector<ll> l(n+1,0),r(n+1,0);
    for (int i = 0;i < n*2;++i) cin >> a[i];
    for (int i = 0;i < n;++i) l[i+1] = l[i]+a[i*2]-a[i*2+1];
    for (int i = n-1;i >= 0;--i) r[i] = r[i+1]+a[i*2+1]-a[i*2];
    ll ans = 0;
    for (int i = 0;i < n+1;++i) ans = max(ans,l[i]+r[i]);
    cout << ans << endl;
}