#include <iostream>

using namespace std;


int main()
{
    int n;
    int cena[21][3];
    int dp[21][3];
    cin >> n;

    for(int i=1; i<=n; i++)
        cin >> cena[i][0] >> cena[i][1] >> cena[i][2];

    int pom, resenie = 20001;

    for(int k = 0; k<3; k++)
    {
        dp[1][k] = cena[1][k];
        dp[1][(k+1)%3] = dp[1][(k+2)%3] = 1000000000;
        for(int i=2; i<=n; i++)
        {
            for(int j=0; j<3; j++)
            {
                dp[i][j] = cena[i][j] + min(dp[i-1][(j+1)%3], dp[i-1][(j+2)%3]);
            }
        }
        pom = min(dp[n][(k+1)%3], dp[n][(k+2)%3]);
        resenie = min(pom, resenie);
    }
    cout << resenie << endl;
    return 0;
}