#pragma GCC optimize("Ofast")
#include <bits/stdc++.h>
using namespace std;
#define REP(i,n) for(int i = 0; i < (int)(n); ++i)
#define ALL(a)  (a).begin(),(a).end()
typedef long long ll;

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int N;
    cin >> N;
    vector<int> A(N+1,0), B(N+1,0);
    REP(i,N-1){
        cin >> A[i] >> B[i];
    }
    int s = accumulate(ALL(A), 0);
    int t = accumulate(ALL(B), 0);
    int ma = 0, mb = 0;
    REP(i,N-1){
        ma = max(ma, A[i]+B[i]-s);
        mb = max(mb, A[i]+B[i]-t);
    }
    cout << min(t-ma,s-mb) + 1 << endl;
    return 0;
}