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/*
 ============================================================================
 Name        : kug.c
 Author      : Paweł Zawada
 ============================================================================
 */

#include <stdio.h>
#include <stdlib.h>
#include <assert.h>

struct s_edge {
	int to_vertex;
	int edge_cost;
	struct s_edge *next_list_node;
};

struct s_edge * *graph;
int *was, n, *previous_on_path, *path_cost, path_len;

int add_edge(int from, int to, int cost) {
	//fprintf(stderr,"Adding edge from %i<-> to %i cost %i\n", from, to, cost);

	struct s_edge *new_edge = (struct s_edge*) malloc(sizeof(struct s_edge));
	new_edge->to_vertex = to;
	new_edge->edge_cost = cost;
	new_edge->next_list_node = graph[from];
	graph[from] = new_edge;

	new_edge = (struct s_edge*) malloc(sizeof(struct s_edge));
	new_edge->to_vertex = from;
	new_edge->edge_cost = cost;
	new_edge->next_list_node = graph[to];
	graph[to] = new_edge;
	return 0;
}

unsigned long long int edge_cost_all() {
	struct s_edge *next_ln;
	unsigned long long int cost = 0;
	int i;
	for (i = 0; i <= n; i++) {
		for (next_ln = graph[i]; next_ln != 0; next_ln =
				next_ln->next_list_node) {
			cost += next_ln->edge_cost;
		}
	}

	return cost/2;
}

int edge_cost(int from, int to) {
	struct s_edge *next_ln = graph[from];
	//fprintf(stderr, "Edge cost %i %i\n", from, to);
	assert(from>=0 && to>=0 && from<=n && to <=n);
	assert(graph[from]);

	for (next_ln = graph[from]; next_ln != 0; next_ln =
			next_ln->next_list_node) {
		if (next_ln->to_vertex == to)
			return (next_ln->edge_cost);
	}
	assert(0);
	return -1;
}

void remove_edge(int from, int to) {
	assert(from>=0 && to>=0 && from<=n && to <=n);
	struct s_edge **next_ln, *tmp;
	if (graph[from] == 0)
		return;

	for (next_ln = &(graph[from]); (*next_ln) != 0;
			next_ln = &((*next_ln)->next_list_node)) {
		if ((*next_ln)->to_vertex == to) {
			tmp = *next_ln;
			*next_ln = (*next_ln)->next_list_node;
			free(tmp);
			return;
		}
	}

}
void remove_edges(int from, int to) {
	//fprintf(stderr, "removing edges from %i to %i\n", from, to);

	assert(from>=0 && to>=0 && from<=n && to <=n);
	remove_edge(from, to);
	remove_edge(to, from);
	//fprintf(stderr,"removed edges\n");
}

void delete_max_from_cycle(int last_on_path, int first_on_cycle) {
	int i, max_cost = -1, max_arg = -1, p_cost;
	assert(last_on_path!=first_on_cycle);
	//fprintf(stderr,"found cycle\n");
	max_cost = edge_cost(last_on_path, first_on_cycle);
	max_arg = first_on_cycle;
	for (i = last_on_path; previous_on_path[i] != -1; i = previous_on_path[i]) {
		p_cost = edge_cost(previous_on_path[i], i);
		if (max_cost < p_cost) {
			max_arg = i;
			max_cost = p_cost;
		}
		//fprintf(stderr,"%i ", i);
	}
	//fprintf(stderr,"->>>>>>>>>>>>>>>>>>> %i ", first_on_cycle);
	//fprintf(stderr,"Max cost: %i \n", max_cost);
	if (max_arg == first_on_cycle)
		remove_edges(last_on_path, first_on_cycle);
	else
		remove_edges(previous_on_path[max_arg], max_arg);
}

int bfs(int from, int edge) {
	int result, s;
	struct s_edge *next_ln;

	//fprintf(stderr,"recursion bfs %i\n", edge);
	if (graph[edge] == 0)
		return -1;

	was[edge] = 1;
	//for (s = 0; s <= n; s++) {
	//	fprintf(stderr,"Was[%i]=%i ", s, was[s]);
	//}
	//fprintf(stderr,"\n");
	for (next_ln = graph[edge]; next_ln != 0; next_ln =
			next_ln->next_list_node) {
		if (next_ln->to_vertex == from)
			continue;
		if (was[next_ln->to_vertex]) {
			delete_max_from_cycle(edge, next_ln->to_vertex);
			return 0;
		} else {
			previous_on_path[next_ln->to_vertex] = edge;
			path_len++;
			result = bfs(edge, next_ln->to_vertex);
			if (result == 0)
				return 0;
		}
	}
	was[edge] = 0;

	return -1;
}

void remove_cycle() {
	int i;
	//fprintf(stderr,"remove cycle\n");
	for (i = 0; i <= n; i++)
		was[i] = 0;
	path_len = 0;
	previous_on_path[0] = -1;
	bfs(-1, 0);
}

int main(void) {
	int i, cost, w, k;
	FILE *inp;
	//fprintf(stderr,"Starting\n");
	/*inp = fopen("kug.in", "r");
	if (inp == 0) {
		fprintf(stderr,"error NULL file\n");
		return -1;
	}*/
	fscanf(stdin, "%i", &n);
	//fprintf(stderr,"%i\n", n);
	graph = (struct s_edge **) malloc((n + 1) * sizeof(struct s_edge*));
	was = (int *) (malloc((n + 1) * sizeof(int)));
	previous_on_path = (int *) (malloc((n + 1) * sizeof(int)));
	for (i = 0; i <= n; i++) {
		graph[i] = 0;
	}

	for (w = 1; w <= n; w++) {
		for (k = 1; k <= n - w + 1; k++) {
			fscanf(stdin, "%i", &cost);
			//fprintf(stderr,"%i ", cost);
			add_edge(w - 1, k + w - 1, cost);
			remove_cycle();
		}
		//fprintf(stderr,"<\n");

	}
	unsigned long long int tot = edge_cost_all();

	printf("%lli\n",tot);
	//printf("%lli ", (unsigned long long int)4000000*1000000000);

	return EXIT_SUCCESS;
}