#include<bits/stdc++.h>
#define int long long
using namespace std;
auto IN = freopen("a.in", "r", stdin);
auto OUT = freopen("a.out", "w", stdout);
auto mread = [](){int x;scanf("%lld", &x);return x;};
const int N = 5e3 + 5;
int n = mread(), t[N], a[N], f[N];
signed main(){
    for(int i = 1; i <= n; i ++){
        cin >> t[i] >> a[i];
    }
    memset(f, 0x3f, sizeof(f));
    f[0] = 0;
    for(int i = 1; i <= n; i ++){
        int ma = a[i];
        for(int j = i - 1; j >= 0; j --){
            int tmp = max(f[j], t[i]);
            f[i] = min(f[i], tmp + ma + ma);
            ma = max(ma, a[j]);
        }
    }
    printf("%lld", f[n]);
    return 0;
}