#include "bits/stdc++.h"
using namespace std;
#define int long long
#define FOR(i, a, b) for(int i=(a);i<(b);i++)
#define RFOR(i, a, b) for(int i=(b-1);i>=(a);i--)
#define REP(i, n) for(int i=0; i<(n); i++)
#define RREP(i, n) for(int i=(n-1); i>=0; i--)
#define ALL(a) (a).begin(),(a).end()
#define UNIQUE_SORT(l) sort(ALL(l)); l.erase(unique(ALL(l)), l.end());
#define CONTAIN(a, b) find(ALL(a), (b)) != (a).end()
#define array2(type, x, y) array<array<type, y>, x>
#define vector2(type) vector<vector<type> >
#define out(...) printf(__VA_ARGS__)

int dxy[] = {0, 1, 0, -1, 0};

void solve();
signed main()
{
#if DEBUG
    std::ifstream in("input.txt");
    std::cin.rdbuf(in.rdbuf());
#endif
    cin.tie(0);
    ios::sync_with_stdio(false);
    solve();
    return 0;
}

/*================================*/
#if DEBUG
#define SIZE 100
#else
#define SIZE 123450
#endif

int N;
int A[20], B[20];

bool ok(int n) {
    REP(i,N) {
        set<int> s;
        REP(j,N) if (j!=i) s.insert(j);
        int base = B[i]-A[i];
        while(!s.empty()) {
            int ma = 0;
            int mj = -1;
            for (int j:s) {
                int l = A[j];

                int d = base + l;
                if (d > n) continue;
                if (ma < d) {
                    ma = d;
                    mj = j;
                }
            }
            if (mj==-1) break;
            base = B[mj]-A[mj];
            s.erase(mj);
        }
        if (s.empty()) {
            return true;
        }
    }
    return false;
}

void solve() {
    cin>>N;
    REP(i,N)cin>>A[i]>>B[i];
    
    int ans = 0;
    RREP(i,12) {
        int n = 1L<<i;
        if (!ok(ans + n)) {
            ans += n;
        }
    }
    
    if (ans==0) ans--;
    cout << ans + 1 << endl;
}