#include <bits/stdc++.h>

using namespace std;

using ll = long long;

const ll INF = 1e17;

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];
    }

    vector<ll> dp(n, INF);
    vector<ll> dp2(n, INF);
    dp[n - 1] = c[n - 1] * 2;
    dp2[n - 1] = c[n - 1];

    for (int i = n - 2; i >= 0; i--) {
        ll minv1 = min(dp2[i + 1], c[i]);
        ll cost1 = dp[i + 1] + d[i + 1] - dp2[i + 1] + minv1 + c[i];
        
        ll minv2 = c[i];
        ll cost2 = dp[i + 1] + 2 * c[i];

        if (cost1 <= cost2) {
            dp[i] = cost1;
            dp2[i] = minv1;
        } else {
            dp[i] = cost2;
            dp2[i] = minv2;
        }
    }
    cout << dp[0] << endl;
    return 0;
}