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

int N, maxn = -1, itmax;
int t[2000006], a[2000006];
int dp[2000006];

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 ++){
		if (a[i] > a[maxn]){
			dp[i] = t[i] + 2 * a[i];
			maxn = i, itmax = -1;
			continue;
		}
		itmax = max(itmax, a[i]);
		dp[i] = t[i] + 2 * a[maxn];
		dp[i] = min(dp[i], max(dp[maxn], t[i]) + 2 * itmax);
//		cout << i << " " << dp[i] << ";;\n";
	}
	printf("%d\n", dp[N]);

    return 0;
}