#define _LIBCPP_DEBUG 0
#include<bits/stdc++.h>
using namespace std;
typedef long long int ll;
ll MOD = 1e9 + 7;



int main(void){

    ll N; cin>>N;
    vector<ll> A(2*N);
    for (int i = 0; i < 2 * N; ++i) {
        cin>>A[i];
    }
    ll sum=0;
    vector<ll> SA(N);
    for (int i = 0; i < N; i++) {
        SA[i] += A[i*2] - A[i*2+1];
    }

    for (int i = 0; i < N; ++i) {
        sum += SA[i];
    }
    ll ans = sum;
    ll sum1 = sum;
    ll sum2 = sum;
    for (int i = 0; i < N; ++i) {
        sum1 = (sum1 - SA[i] - SA[i]) ;
        ans = max(ans, sum1);
    }

    for (int i = N-1; i >= 0; --i) {
        sum2 = (sum2 - SA[i]-SA[i]);
        ans = max(ans,sum2);
    }

    cout<<ans<<endl;

}