1149.cpp

#include <iostream>
using namespace std;

const int MAX = 1000;
int N;
int d[4][MAX + 1];
int house[4][MAX + 1]; // [1] : red, [2] : green, [3] : blue

int main(void)
{
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    cin >> N;
    for (int i = 1; i <= N; i++) {
        cin >> house[1][i] >> house[2][i] >> house[3][i];
    }

    for (int i = 1; i <= N; i++) {
        d[1][i] = min(d[2][i - 1], d[3][i - 1]) + house[1][i];
        d[2][i] = min(d[1][i - 1], d[3][i - 1]) + house[2][i];
        d[3][i] = min(d[2][i - 1], d[1][i - 1]) + house[3][i];
    }

    cout << min(d[3][N], min(d[1][N], d[2][N])) << '\n';
    return 0;
}