#include<bits/stdc++.h>
#pragma GCC optimize(2)
using namespace std;

int N, maxn = -1, itmax;
int t[2000006], a[2000006];
int dp[2000006];
stack<int> stk;

int main(){
#ifndef ONLINE_JUDGE
    freopen("../data.in", "r", stdin);
    freopen("../data.out", "w", stdout);
#endif

	scanf("%d", &N);
	for (int i = 1; i <= N; i ++){
		scanf("%d %d", &t[i], &a[i]);
	}
	memset(dp, 0x3f, sizeof(dp));
	dp[0] = 0;
	for (int i = 1; i <= N; i ++){
		while (stk.size() && a[stk.top()] <= a[i]) stk.pop();
		if (!stk.size()){
			stk.push(i);
			dp[i] = t[i] + 2 * a[i];
			continue;
		}
		dp[i] = max(t[i], dp[stk.top()]) + 2 * a[i];
		if (dp[i] - dp[stk.top()] < 2 * (a[stk.top()] - a[i])) stk.push(i);
	}
	printf("%d\n", dp[N]);

    return 0;
}