#include <bits/stdc++.h>
using namespace std;
#define ll long long int
#define vll vector<ll>
#define vpll vector<pair<ll,ll>>
#define vpi vector<pair<int,int>>
#define fr first
#define sc second
#define f(i, x) for(ll i=0; i<x; i++)
#define revn(i, x) for (ll i = x - 1; i >= 0; i--)
#define rp(i,le,ri) for(ll i=le;i<ri;i++)
#define rrp(i,ri,le) for(ll i=ri;i>=le;i--)
#define asort(o) sort((o).begin(), (o).end())
#define dsort(o) sort((o).rbegin(), (o).rend())
#define minhp priority_queue<ll, vector<ll>, greater<>>
#define revhp priority_queue<ll>
typedef pair<int, int> p;
inline ll lcm(ll m,ll n) {return(m*n/__gcd(m,n));}
const int MOD=1e9+7;
const ll INF = INT_MAX, INF2 = LLONG_MAX - 1;
bool cmp(const p &a, const p &b)
{
    return a.fr <= b.fr;
}
int binarySearch(int arr[], int low, int high, int x)
{
    while (low <= high) {
        int mid = low + (high - low) / 2;
        if (arr[mid] == x)
            return mid;
        if (arr[mid] < x)
        low = mid + 1;
        else
            high = mid - 1;
    }
    return -1;
}
vector<bool> v;
vector<vector<int> > g;
void edge(int a, int b)
{
g[a].push_back(b);
}
void bfs(int u)
{
    queue<int> q;
    q.push(u);
    v[u] = true;
    while (!q.empty()) {
        int f = q.front();
        q.pop();
        cout << f << ' ';
        for (auto i = g[f].begin(); i != g[f].end(); i++) {
            if (!v[*i]) {
                q.push(*i);
                v[*i] = true;
            }
        }
    }
}
void dfs(int v, vector<vector<int>>& adj, vector<bool>& visited) {
    visited[v] = true;
    for (int u : adj[v]) {
        if (!visited[u]) {
            dfs(u, adj, visited);
        }
    }
}
int mex(vector<int> const& A, int l, int r) {
    set<int> b(A.begin() + l, A.begin() + r + 1);
    int result = 0;
    while (b.count(result)) ++result;
    return result;
}
int main()
{
    ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
    int n;
    cin>>n;
    int ar[n][2];
    f(j, n)
    cin>>ar[j][0]>>ar[j][1];
    int dp[n][2];
    dp[0][0]=ar[0][0];
    dp[0][1]=ar[0][1];
    for(int j=1; j<n; j++)
    {
        dp[j][0]=min(dp[j-1][0]+ar[j][0], max(dp[j-1][1], ar[j][0]));
        dp[j][1]=min(dp[j-1][1]+ar[j][1], max(dp[j-1][0], ar[j][1]));
    }
    int ans=min(dp[n-1][0], dp[n-1][1]);
    cout<<ans<<endl;
}