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#include <iostream>
#include <fstream>
#include <vector>
#include <algorithm>
#include <climits>

using namespace std;

int main() {
    ifstream fin("input.txt");
    ofstream fout("output.txt");

    int n;
    fin >> n;
    vector<int> dp(n, INT_MAX);
    vector<int> coast(3);
    fin >> dp[0] >> dp[1] >> dp[2];
    for (int i = 1; i < n; i++) {
        fin >> coast[0] >> coast[1] >> coast[2];
        for (int j = i; j < i + 3 && j < n; j++)
            dp[j] = min(dp[j], dp[i - 1] + coast[j-i]);
    }
    fout << dp[n - 1] << endl;

    fin.close();
    fout.close();
    return 0;
}