#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#define graph_valtype int
#define heap_valtype pair
#define inf (1e18)

typedef struct {
	int v_num;
	double dis;
}pair;

int compare(heap_valtype a, heap_valtype b){
	if(a.dis < b.dis){
		return -1;
	}
	else if(a.dis == b.dis){
		return 0;
	}
	else{
		return 1;
	}
}


typedef struct graph_edge_sub graph_edge;

typedef struct {
	int num;
	int next_num;
	graph_edge *next;
	int prev_num;
}graph_vertex_sub;

struct graph_edge_sub{
	graph_vertex_sub *v;
	double w;
	graph_edge *next;
};

typedef struct graph_v_sub graph_vertex;

struct graph_v_sub{
	int num;
	graph_valtype val;
	int next_num;
	graph_vertex **next;
	double *next_weight;
	int prev_num;
	graph_vertex **prev;
	double *prev_weight;
};

typedef struct {
	int N;
	graph_vertex_sub **v_s;
	graph_vertex **v;
}graph;

//頂点数N, 各頂点の初期値ini_valのグラフを作る
graph *make_graph(int N, graph_valtype ini_val){
	int i;
	graph *g = (graph *)malloc(sizeof(graph));
	g->N = N;
	g->v_s = (graph_vertex_sub **)malloc(sizeof(graph_vertex_sub *) * N);
	g->v = (graph_vertex **)malloc(sizeof(graph_vertex *) * N);
	for(i = 0; i < N; i++){
		(g->v_s)[i] = (graph_vertex_sub *)malloc(sizeof(graph_vertex_sub));
		(g->v_s)[i]->num = i;
		(g->v_s)[i]->next_num = 0;
		(g->v_s)[i]->next = NULL;
		(g->v_s)[i]->prev_num = 0;
		(g->v)[i] = (graph_vertex *)malloc(sizeof(graph_vertex));
		(g->v)[i]->num = i;
		(g->v)[i]->val = ini_val;
		(g->v)[i]->next_num = 0;
		(g->v)[i]->next = NULL;
		(g->v)[i]->next_weight = NULL;
		(g->v)[i]->prev_num = 0;
		(g->v)[i]->prev = NULL;
		(g->v)[i]->prev_weight = NULL;
	}
	return g;
}

//グラフgの頂点aから頂点bに重みwの有向辺を張る (0 <= a, b <= N - 1)
void set_edge_graph(int a, int b, double w, graph *g){
	graph_edge *new1 = (graph_edge *)malloc(sizeof(graph_edge));
	new1->v = (g->v_s)[b];
	new1->w = w;
	new1->next = (g->v_s)[a]->next;
	(g->v_s)[a]->next = new1;
	(g->v_s)[a]->next_num++;
	(g->v_s)[b]->prev_num++;
}

//set_edge_graph後に呼び出す
void build_graph(graph *g){
	int i;
	graph_vertex_sub **v_s = g->v_s;
	graph_vertex **v = g->v;
	graph_vertex *nowv;
	graph_edge *nowe;
	for(i = 0; i < g->N; i++){
		v[i]->next = (graph_vertex **)malloc(sizeof(graph_vertex *) * v_s[i]->next_num);
		v[i]->next_weight = (double *)malloc(sizeof(double) * v_s[i]->next_num);
		v[i]->prev = (graph_vertex **)malloc(sizeof(graph_vertex *) * v_s[i]->prev_num);
		v[i]->prev_weight = (double *)malloc(sizeof(double) * v_s[i]->prev_num);
	}
	for(i = 0; i < g->N; i++){
		nowv = v[i];
		for(nowe = v_s[i]->next; nowe != NULL; nowe = nowe->next){
			(nowv->next)[nowv->next_num] = v[nowe->v->num];
			(nowv->next_weight)[nowv->next_num] = nowe->w;
			nowv->next_num++;
			(v[nowe->v->num]->prev)[v[nowe->v->num]->prev_num] = nowv;
			(v[nowe->v->num]->prev_weight)[v[nowe->v->num]->prev_num] = nowe->w;
			v[nowe->v->num]->prev_num++;
		}
	}
}

typedef struct heap_node_sub{
	heap_valtype val;
	struct heap_node_sub *parent;
	struct heap_node_sub *prev;
	struct heap_node_sub *next;
	struct heap_node_sub *left;
	struct heap_node_sub *right;
}heap_node;

typedef struct {
	int N;
	heap_node *root;
	heap_node *last;
}heap;

//heapを生成
heap *make_heap(){
	heap *h = (heap *)malloc(sizeof(heap));
	h->N = 0;
	h->root = NULL;
	h->last = NULL;
	return h;
}

int element_num_heap(heap *h){
	return h->N;
}

void up_heapify(heap_node *n, heap *h){
	if(n->parent != NULL){
		if(compare(n->val, n->parent->val) < 0){
			heap_valtype tmp;
			tmp = n->val;
			n->val = n->parent->val;
			n->parent->val = tmp;
			up_heapify(n->parent, h);
		}
	}
}

//データを追加
void add_data_heap(heap_valtype val, heap *h){
	heap_node *new = (heap_node *)malloc(sizeof(heap_node));
	new->val = val;
	new->next = NULL;
	new->left = NULL;
	new->right = NULL;
	if(element_num_heap(h) == 0){
		new->parent = NULL;
		new->prev = NULL;
		h->root = new;
		h->last = new;
	}
	else if(element_num_heap(h) == 1){
		new->parent = h->root;
		new->prev = h->root;
		h->root->left = new;
		h->root->next = new;
		h->last = new;
		up_heapify(new, h);
	}
	else{
		new->prev = h->last;
		h->last->next = new;
		if(h->last->parent->right == NULL){
			new->parent = h->last->parent;
			h->last->parent->right = new;
		}
		else{
			new->parent = h->last->parent->next;
			h->last->parent->next->left = new;
		}
		h->last = new;
		up_heapify(new, h);
	}
	h->N++;
}

void down_heappify(heap_node *n, heap *h){
	if(n->left != NULL){
		heap_valtype tmp;
		if(n->right == NULL){
			if(compare(n->val, n->left->val) > 0){
				tmp = n->val;
				n->val = n->left->val;
				n->left->val = tmp;
				down_heappify(n->left, h);
			}
		}
		else{
			if(compare(n->left->val, n->right->val) <= 0 && compare(n->val, n->left->val) > 0){
				tmp = n->val;
				n->val = n->left->val;
				n->left->val = tmp;
				down_heappify(n->left, h);
			}
			else if(compare(n->left->val, n->right->val) > 0 && compare(n->val, n->right->val) > 0){
				tmp = n->val;
				n->val = n->right->val;
				n->right->val = tmp;
				down_heappify(n->right, h);
			}
		}
	}
}

//最小のものを取り出す
heap_valtype take_min_heap(heap *h){
	if(element_num_heap(h) == 0){
		printf("no data in the heap\n");
	}
	heap_valtype ans = h->root->val;
	heap_node *ln = h->last;
	if(element_num_heap(h) == 1){
		h->root = NULL;
		h->last = NULL;
	}
	else{
		ln->prev->next = NULL;
		if(ln->parent->right == NULL){
			ln->parent->left = NULL;
		}
		else{
			ln->parent->right = NULL;
		}
		h->last = ln->prev;
		h->root->val = ln->val;
		down_heappify(h->root, h);
	}
	free(ln);
	h->N--;
	return ans;
}

heap_valtype look_min_heap(heap *h){
	if(element_num_heap(h) == 0){
		printf("no data in the heap\n");
	}
	return h->root->val;
}

double *Dijkstra(graph *g, int s){
	int N = g->N, i;
	double *distance = (double *)malloc(sizeof(double) * N);
	for(i = 0; i < N; i++){
		distance[i] = inf;
	}
	heap *h = make_heap();
	pair p;
	p.v_num = s;
	p.dis = 0;
	add_data_heap(p, h);
	graph_vertex *nowv;
	while(element_num_heap(h) > 0){
		p = take_min_heap(h);
		nowv = g->v[p.v_num];
		if(p.dis < distance[nowv->num]){
			distance[nowv->num] = p.dis;
			for(i = 0; i < nowv->next_num; i++){
				p.v_num = nowv->next[i]->num;
				p.dis = distance[nowv->num] + nowv->next_weight[i];
				add_data_heap(p, h);
			}
		}
	}
	return distance;
}

double max(double a, double b){
	return a >= b ? a : b;
}

int main(){
	int N, i, j;
	double xs, ys, xt, yt;
	scanf("%lf%lf%lf%lf", &xs, &ys, &xt, &yt);
	scanf("%d", &N);
	double *x = (double *)malloc(sizeof(double) * (N + 2));
	double *y = (double *)malloc(sizeof(double) * (N + 2));
	double *r = (double *)malloc(sizeof(double) * (N + 2));
	x[0] = xs;
	y[0] = ys;
	r[0] = 0;
	for(i = 1; i <= N; i++){
		scanf("%lf%lf%lf", &x[i], &y[i], &r[i]);
	}
	x[N + 1] = xt;
	y[N + 1] = yt;
	r[N + 1] = 0;
	graph *g = make_graph(N + 2, 0);
	for(i = 0; i <= N + 1; i++){
		for(j = 0; j <= N + 1; j++){
			if(i != j){
				set_edge_graph(i, j, max(hypot(x[i] - x[j], y[i] - y[j]) - (r[i] + r[j]), 0), g);
			}
		}
	}
	build_graph(g);
	printf("%.12lf\n", Dijkstra(g, 0)[N + 1]);
	return 0;
}

Measured memory_bytes: 125056