#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 REP1(i, n) for(int i=1; i<=(n); i++)
#define RREP1(i, n) for(int i=(n); i>=1; 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 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,A,B,a,b;

void solve() {
    cin>>N;
    A=B=0;
    REP(i,N-1) {
        cin>>a>>b;
        A+=a;
        B+=b;
    }
    int diff = A-B;
    int maxa = B;
    int maxb = A;
    int mina, minb;
    if (diff < 0) {
        // 1駅は、入った人(a)の方が多い
        mina = -diff;
        minb = 0;
    } else {
        // 1駅は、出た人(b)の方が多い
        minb = diff;
        mina = 0;
    }
    int ans = min(maxa-mina, maxb-minb)+1;
    cout << ans << endl;
}