#include<bits/stdc++.h>
#define int long long
#define fi first
#define se second
#define mp make_pair
using namespace std;
//#define fin cin
//#define fout cout
ifstream fin("task.in");
ofstream fout("task.out");
auto mread = [](){
    int x;
    fin >> x;
    return x;
};
const int N = 2005;
int n = mread(), a[N], b[N], s[N][2];
pair<int, int> f[N][2];
signed main(){
    for(int i = 1; i <= n; i ++){
        a[i] = mread(), b[i] = mread();
        s[i][0] = s[i - 1][0] + a[i];
        s[i][1] = s[i - 1][1] + b[i];
    }
    for(int i = 1; i <= n; i ++)
    f[i][0] = f[i][1] = mp(LONG_LONG_MAX, 0);
    f[0][0] = f[0][1] = mp(0, 0);
    for(int i = 1; i <= n; i ++){
        for(int j = 1; j <= i; j ++){
            int sum = s[i][0] - s[j - 1][0];
            int tmp = f[j - 1][0].fi + sum;
            f[i][0] = min(f[i][0], mp(tmp, max(f[j - 1][0].se, tmp - a[i])));
            tmp = f[j - 1][1].se + sum;
            if(tmp >= f[j - 1][1].fi){
                f[i][0] = min(f[i][0], mp(tmp, max(f[j - 1][1].fi, tmp - a[i])));
            }
            if(tmp <= f[j - 1][1].fi){
                f[i][1] = min(f[i][1], mp(f[j - 1][1].fi, max(tmp, f[j - 1][1].se)));
            }
            
            sum = s[i][1] - s[j - 1][1];
            tmp = f[j - 1][1].fi + sum;
            f[i][1] = min(f[i][1], mp(tmp, max(f[j - 1][1].se, tmp - b[i])));
            tmp = f[j - 1][0].se + sum;
            if(tmp >= f[j - 1][0].fi){
                f[i][1] = min(f[i][1], mp(tmp, max(f[j - 1][0].fi, tmp - b[i])));
            }
            if(tmp <= f[j - 1][0].fi){
                f[i][0] = min(f[i][0], mp(f[j - 1][0].fi, max(tmp, f[j - 1][0].se)));
            }
        }
    }
    fout << min(f[n][0].fi, f[n][1].fi);
}