#include <cstdio>
#include <vector>
#include <algorithm>
#include <list>
using namespace std;
int n;
long long t[2000010], a[2000010];
long long dp[2000010];
vector<long long> pos;
list<long long> dq;
long long calc(long long x) {
    return dp[x] + 2 * a[x + 1];
}
int main() {
    scanf("%d", &n);
    for (int i = 1; i <= n; i++) {
        scanf("%lld%lld", &t[i], &a[i]);
    }
    for (int i = n; i >= 1; i--) {
        a[i] = max(a[i], a[i + 1]);
        if (a[i] != a[i + 1]) {
            pos.push_back(i);
        }
    }
    pos.push_back(0);
    reverse(pos.begin(), pos.end());
    dp[0] = 0;
    dq.push_back(0);
    int now = 0;
    for (int id = 1; id < pos.size(); id++) {
        int i = pos[id];
        while (!dq.empty() && dp[dq.front()] <= t[i]) {
            // printf("dp[%d] = %d <= %d\n", dq.front(), dp[dq.front()], t[i]);
            now = dq.front();
            dq.pop_front();
        }
        // printf("%d : now=%d\n", i, now);
        dp[i] = 1e18;
        dp[i] = min(dp[i], t[i] + 2 * a[now + 1]);
        if (!dq.empty()) {
            dp[i] = min(dp[i], calc(dq.front()));
        }
        while (!dq.empty() && calc(dq.back()) > calc(i)) {
            dq.pop_back();
        }
        dq.push_back(i);
        // printf("%d : %d\n", i, dp[i]);
    }
    printf("%lld\n", dp[n]);
    return 0;
}