#include <iomanip>
#include <iostream>
#include <functional>
#include <algorithm>
#include <math.h>
#include <cmath>
#include <string>
#include <cstring>
#include <vector>
#include<set>
#include<map>
#include <time.h>
#include <fstream>
typedef long long ll;
using namespace std;
int a[3][200002];
int n;
/*
4
13 7 5
7 13 6
14 3 12
15 6 16
0
*/

ll dp[3][200002];
ll solve(int x, int y){
	if (x == 1 && y == n - 1){
		return a[x][y];
	}
	else if (x<0 || x>2 || y >= n)return (1<<22);
	ll ret = (1 << 22);
	if (dp[x][y] != -1)return dp[x][y];
		ret = min(a[x][y] + solve(x + 1, y), ret);
		ret = min(a[x][y] + solve(x + 1, y + 1), ret);
		ret = min(a[x][y] + solve(x - 1, y + 1), ret);
		ret = min(a[x][y] + solve(x, y + 1),ret);
		dp[x][y] = ret;
	return ret;
}
int main(){
	while (1)
	{

		cin >> n;
		if (n== 0)return 0;

		for (int i = 0; i < n; i++)
		{
			for (int j = 0; j < 3; j++)
			{
				cin >> a[j][i];
			}
		}
		memset(dp, -1, sizeof (dp));
		cout << solve(1, 0);









	}
}