#include <bits/stdc++.h>

using namespace std;

using ll = long long;

const ll INF = 1e17;

// dp[その日で最初？][手数料支払い済み？]
ll dp[2][2] = {{0, INF}, {INF, INF}};

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    int n;
    cin >> n;
    vector<ll> c(n), d(n);
    for (int i = 0; i < n; i++) {
        cin >> c[i] >> d[i];
    }

    ll ans = 0;
    for (int i = n - 1; i >= 0; i--) {
        ans += c[i];

        ll ndp[2][2] = {{INF, INF}, {INF, INF}};

        ndp[0][0] = min(ndp[0][0], min(dp[0][0], dp[1][1]) + d[i]);
        ndp[0][1] = min({ndp[0][1], min(dp[0][0], dp[1][1]) + d[i] + c[i], dp[0][1] + d[i]});
        ndp[1][1] = min({ndp[1][1], min(dp[0][0], dp[1][1]) + c[i], dp[0][1]});

        dp[0][0] = ndp[0][0];
        dp[0][1] = ndp[0][1];
        dp[1][1] = ndp[1][1];
    }
    
    ans += dp[1][1];
    cout << ans << endl;
    return 0;
}