#include<bits/stdc++.h>
#pragma GCC optimize(2)
#define query(l, r) (max(st[__lg(r - l + 1)][l], st[__lg(r - l + 1)][r - (1 << (__lg(r - l + 1))) + 1]))
using namespace std;

int N, maxn = -1, itmax;
int t[2000006], a[2000006];
long long dp[2000006];
int st[25][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]);
		st[0][i] = a[i];
	}
	for (int j = 1; j <= __lg(N); j ++){
		for (int i = 1; i + (1 << j) <= N + 1; i ++){
			st[j][i] = max(st[j - 1][i], st[j - 1][i + (1 << (j - 1))]);
		}
	}
	memset(dp, 0x3f, sizeof(dp));
	dp[0] = 0;
	for (int i = 1; i <= N; i ++){
		for (int j = 0; j < i; j ++){
			dp[i] = min(dp[i], max(dp[j], 1LL * t[i]) + 2LL * query((j + 1), i));
		}
	}
	printf("%lld\n", dp[N]);

    return 0;
}