#include<bits/stdc++.h>
#include<cmath>
using namespace std;

int a[100010][100010];
int dp[200000];
int main(){
	int n;
	cin >> n;
	for(int i = 1; i <= n; i++){
		for(int j = i+1;j<=n;j++){
			cin >> a[i][j]; 
			dp[i] = 1e9;
			dp[i] = min(dp[i], a[i][j] +dp[i]);
		}
	}
	cout << dp[n];
	
	return 0;
}