Problem:
Score : 600 points

Problem Statement

On the xy-plane, Snuke is going to travel from the point (x_s, y_s) to the point (x_t, y_t).
He can move in arbitrary directions with speed 1.
Here, we will consider him as a point without size.

There are N circular barriers deployed on the plane.
The center and the radius of the i-th barrier are (x_i, y_i) and r_i, respectively.
The barriers may overlap or contain each other.

A point on the plane is exposed to cosmic rays if the point is not within any of the barriers.

Snuke wants to avoid exposure to cosmic rays as much as possible during the travel.
Find the minimum possible duration of time he is exposed to cosmic rays during the travel.

Constraints

All input values are integers.

-10^9 ≤ x_s, y_s, x_t, y_t ≤ 10^9

(x_s, y_s) ≠ (x_t, y_t)

1≤N≤1,000

-10^9 ≤ x_i, y_i ≤ 10^9

1 ≤ r_i ≤ 10^9

Input

The input is given from Standard Input in the following format:

x_s y_s x_t y_t
N
x_1 y_1 r_1
x_2 y_2 r_2
:
x_N y_N r_N

Output

Print the minimum possible duration of time Snuke is exposed to cosmic rays during the travel.
The output is considered correct if the absolute or relative error is at most 10^{-9}.

Sample Input 1

-2 -2 2 2
1
0 0 1

Sample Output 1

3.6568542495

An optimal route is as follows:

Sample Input 2

-2 0 2 0
2
-1 0 2
1 0 2

Sample Output 2

0.0000000000

An optimal route is as follows:

Sample Input 3

4 -2 -2 4
3
0 0 2
4 0 1
0 4 1

Sample Output 3

4.0000000000

An optimal route is as follows:

Solution in Java8 (OpenJDK 1.8.0) (judge verdict: Accepted)

import java.util.*;
import java.io.*;
import java.math.*;
public class Main {
	static boolean DEBUG;
	public static void main(String[] args) {
		DEBUG = args.length > 0 && args[0].equals("-DEBUG");
		Solver solver = new Solver();
		solver.solve();
		solver.exit();
	}

	static class FastScanner {
		private final InputStream in = System.in;
		private final byte[] buffer = new byte[1024];
		private int ptr = 0;
		private int buflen = 0;
		private boolean hasNextByte() {
			if(ptr < buflen) {
				return true;
			}else{
				ptr = 0;
				try {
					buflen = in.read(buffer);
				} catch (IOException e) {
					e.printStackTrace();
				}
				if(buflen <= 0) {
					return false;
				}
			}
			return true;
		}
		private int readByte() { if(hasNextByte()) return buffer[ptr++]; else return -1;}
		private boolean isPrintableChar(int c) { return 33 <= c && c <= 126;}
		private void skipUnprintable() { while(hasNextByte() && !isPrintableChar(buffer[ptr])) ptr++;}
		public boolean hasNext() { skipUnprintable(); return hasNextByte();}
		public String next() {
			if(!hasNext()) throw new NoSuchElementException();
			StringBuilder sb = new StringBuilder();
			int b = readByte();
			while(isPrintableChar(b)) {
				sb.appendCodePoint(b);
				b = readByte();
			}
			return sb.toString();
		}
		public long nextLong() {
			if(!hasNext()) throw new NoSuchElementException();
			long n = 0;
			boolean minus = false;
			int b = readByte();
			if(b == '-') {
				minus = true;
				b = readByte();
			}
			if(b < '0' || '9' < b) {
				throw new NumberFormatException();
			}
			while(true){
				if('0' <= b && b <= '9') {
					n *= 10;
					n += b - '0';
				}else if(b == -1 || !isPrintableChar(b)){
					return minus ? -n : n;
				}else{
					throw new NumberFormatException();
				}
				b = readByte();
			}
		}
	}

	static class Solver {
		FastScanner sc = new FastScanner();
		public Solver() { }

		String ns() { return sc.next(); }
		String[] ns(int n) {
			String a[] = new String[n];
			for(int i = 0; i < n; i ++) { a[i] = ns(); }
			return a;
		}
		String[][] ns(int n, int m) {
			String a[][] = new String[n][m];
			for(int i = 0; i < n; i ++) { a[i] = ns(m); }
			return a;
		}
		char[] nc(int n) {
			String str = ns();
			char a[] = new char[max(n, str.length())];
			for(int i = 0; i < str.length(); i ++) { a[i] = str.charAt(i); }
			return a;
		}
		char[][] nc(int n, int m) {
			char a[][] = new char[n][m];
			for(int i = 0; i < n; i ++) { a[i] = nc(m); }
			return a;
		}
		boolean[] nb(int n, char t) {
			char c[] = nc(-1);
			if(n < 0) n = c.length;
			boolean a[] = new boolean[n];
			for(int i = 0; i < n; i ++) { a[i] = c[i] == t; }
			return a;
		}
		boolean[][] nb(int n, int m, char t) {
			boolean a[][] = new boolean[n][m];
			for(int i = 0; i < n; i ++) { a[i] = nb(m, t); }
			return a;
		}
		int ni() { return (int)sc.nextLong(); }
		int[] ni(int n) {
			int a[] = new int[n];
			for(int i = 0; i < n; i ++) { a[i] = ni(); }
			return a;
		}
		int[][] ni(int n, int m) {
			int a[][] = new int[n][m];
			for(int i = 0; i < n; i ++) { a[i] = ni(m); }
			return a;
		}
		long nl() { return sc.nextLong(); }
		long[] nl(int n) {
			long a[] = new long[n];
			for(int i = 0; i < n; i ++) { a[i] = nl(); }
			return a;
		}
		long[][] nl(int n, int m) {
			long a[][] = new long[n][m];
			for(int i = 0; i < n; i ++) { a[i] = nl(m); }
			return a;
		}
		double nd() { return Double.parseDouble(sc.next()); }
		double[] nd(int n) {
			double a[] = new double[n];
			for(int i = 0; i < n; i ++) { a[i] = nd(); }
			return a;
		}
		double[][] nd(int n, int m) {
			double a[][] = new double[n][m];
			for(int i = 0; i < n; i ++) { a[i] = nd(m); }
			return a;
		}

		PrintWriter out = new PrintWriter(System.out);
		PrintWriter err = new PrintWriter(System.err);
		void prt() { out.print(""); }
		<T> void prt(T a) { out.print(a); }
		void prtln() { out.println(""); }
		<T> void prtln(T a) { out.println(a); }
		void prtln(int... a) {
			StringBuilder sb = new StringBuilder();
			for(int element : a){ sb.append(element+" "); }
			prtln(sb.toString().trim());
		}
		void prtln(long... a) {
			StringBuilder sb = new StringBuilder();
			for(long element : a){ sb.append(element+" "); }
			prtln(sb.toString().trim());
		}
		void prtln(double... a) {
			StringBuilder sb = new StringBuilder();
			for(double element : a){ sb.append(element+" "); }
			prtln(sb.toString().trim());
		}
		void prtln(String... a) {
			StringBuilder sb = new StringBuilder();
			for(String element : a){ sb.append(element+" "); }
			prtln(sb.toString().trim());
		}
		void prtln(char... a) {
			StringBuilder sb = new StringBuilder();
			for(char element : a){ sb.append(element); }
			prtln(sb.toString().trim());
		}
		void prtln(int[][] a) { for(int[] element : a){ prtln(element); } }
		void prtln(long[][] a) { for(long[] element : a){ prtln(element); } }
		void prtln(double[][] a) { for(double[] element : a){ prtln(element); } }
		void prtln(String[][] a) { for(String[] element : a){ prtln(element); } }
		void prtln(char[][] a) { for(char[] element : a){ prtln(element); } }
		String errconvert(int a) { return isINF(a) ? "_" : String.valueOf(a); }
		String errconvert(long a) { return isINF(a) ? "_" : String.valueOf(a); }
		void errprt(int a) { if(DEBUG) { err.print(errconvert(a)); } }
		void errprt(long a) { if(DEBUG) { err.print(errconvert(a)); } }
		void errprt() { if(DEBUG) { err.print(""); } }
		<T> void errprt(T a) { if(DEBUG) { err.print(a); } }
		void errprt(boolean a) { if(DEBUG) { errprt(a ? "#" : "."); } }
		void errprtln() { if(DEBUG) { err.println(""); } }
		void errprtln(int a) { if(DEBUG) { err.println(errconvert(a)); } }
		void errprtln(long a) { if(DEBUG) { err.println(errconvert(a)); } }
		<T> void errprtln(T a) { if(DEBUG) { err.println(a); } }
		void errprtln(boolean a) { if(DEBUG) { errprtln(a ? "#" : "."); } }
		void errprtln(int... a) {
			if(DEBUG) {
				StringBuilder sb = new StringBuilder();
				for(int element : a){ sb.append(errconvert(element)+" "); }
				errprtln(sb.toString().trim());
			}
		}
		void errprtln(long... a) {
			if(DEBUG) {
				StringBuilder sb = new StringBuilder();
				for(long element : a){ sb.append(errconvert(element)+" "); }
				errprtln(sb.toString().trim());
			}
		}
		void errprtln(double... a) {
			if(DEBUG) {
				StringBuilder sb = new StringBuilder();
				for(double element : a){ sb.append(element+" "); }
				errprtln(sb.toString().trim());
			}
		}
		void errprtln(String... a) {
			if(DEBUG) {
				StringBuilder sb = new StringBuilder();
				for(String element : a){ sb.append(element+" "); }
				errprtln(sb.toString().trim());
			}
		}
		void errprtln(char... a) {
			if(DEBUG) {
				StringBuilder sb = new StringBuilder();
				for(char element : a){ sb.append(element); }
				errprtln(sb.toString().trim());
			}
		}
		void errprtln(boolean... a) {
			if(DEBUG) {
				StringBuilder sb = new StringBuilder();
				for(boolean element : a){ sb.append((element ? "#" : ".")+" "); }
				errprtln(sb.toString().trim());
			}
		}
		void errprtln(int[][] a) { if(DEBUG) { for(int[] element : a){ errprtln(element); } } }
		void errprtln(long[][] a) { if(DEBUG) { for(long[] element : a){ errprtln(element); } } }
		void errprtln(double[][] a) { if(DEBUG) { for(double[] element : a){ errprtln(element); } } }
		void errprtln(String[][] a) { if(DEBUG) { for(String[] element : a){ errprtln(element); } } }
		void errprtln(char[][] a) { if(DEBUG) { for(char[] element : a){ errprtln(element); } } }
		void errprtln(boolean[][] a) { if(DEBUG) { for(boolean[] element : a){ errprtln(element); } } }

		void reply(boolean b) { prtln(b ? "Yes" : "No"); }
		void REPLY(boolean b) { prtln(b ? "YES" : "NO"); }

		void flush() { out.flush(); if(DEBUG) { err.flush(); } }
		void exit() { flush(); System.exit(0); }
		void assertion(boolean b) { if(!b) throw new AssertionError(); }

		int min(int a, int b) { return Math.min(a, b); }
		long min(long a, long b) { return Math.min(a, b); }
		double min(double a, double b) { return Math.min(a, b); }
		int min(int... x) {
			int min = x[0];
			for(int val : x) { min = min(min, val); }
			return min;
		}
		long min(long... x) {
			long min = x[0];
			for(long val : x) { min = min(min, val); }
			return min;
		}
		double min(double... x) {
			double min = x[0];
			for(double val : x) { min = min(min, val); }
			return min;
		}
		int max(int a, int b) { return Math.max(a, b); }
		long max(long a, long b) { return Math.max(a, b); }
		double max(double a, double b) { return Math.max(a, b); }
		int max(int... x) {
			int max = x[0];
			for(int val : x) { max = max(max, val); }
			return max;
		}
		long max(long... x) {
			long max = x[0];
			for(long val : x) { max = max(max, val); }
			return max;
		}
		double max(double... x) {
			double max = x[0];
			for(double val : x) { max = max(max, val); }
			return max;
		}
		long sum(int... a) {
			long sum = 0;
			for(int element : a) { sum += element; }
			return sum;
		}
		long sum(long... a) {
			long sum = 0;
			for(long element : a) { sum += element; }
			return sum;
		}
		double sum(double... a) {
			double sum = 0;
			for(double element : a) { sum += element; }
			return sum;
		}
		long[] sums(int[] a) {
			long sum[] = new long[a.length + 1];
			sum[0] = 0;
			for(int i = 0; i < a.length; i ++) { sum[i + 1] = sum[i] + a[i]; }
			return sum;
		}
		long[] sums(long[] a) {
			long sum[] = new long[a.length + 1];
			sum[0] = 0;
			for(int i = 0; i < a.length; i ++) { sum[i + 1] = sum[i] + a[i]; }
			return sum;
		}
		double[] sums(double[] a) {
			double sum[] = new double[a.length + 1];
			sum[0] = 0;
			for(int i = 0; i < a.length; i ++) { sum[i + 1] = sum[i] + a[i]; }
			return sum;
		}

		int abs(int x) { return x >= 0 ? x : - x; }
		long abs(long x) { return x >= 0 ? x : - x; }
		double abs(double x) { return x >= 0 ? x : - x; }
		int signum(int x) { return x > 0 ? 1 : x < 0 ? -1 : 0; }
		int signum(long x) { return x > 0 ? 1 : x < 0 ? -1 : 0; }
		int signum(double x) { return x > 0 ? 1 : x < 0 ? -1 : 0; }
		long round(double x) { return Math.round(x); }
		long floor(double x) { return (long)Math.floor(x); }
		int divfloor(int a, int b) { return signum(a) == signum(b) ? a / b : - divceil(abs(a), abs(b)); }
		long divfloor(long a, long b) { return signum(a) == signum(b) ? a / b : - divceil(abs(a), abs(b)); }
		long ceil(double x) { return (long)Math.ceil(x); }
		int divceil(int a, int b) { return a >= 0 && b > 0 ? (a + b - 1) / b
											: a < 0 && b < 0 ? divceil(abs(a), abs(b))
											: - divfloor(abs(a), abs(b)); }
		long divceil(long a, long b) { return a >= 0 && b > 0 ? (a + b - 1) / b
											: a < 0 && b < 0 ? divceil(abs(a), abs(b))
											: - divfloor(abs(a), abs(b)); }
		double sqrt(int x) { return Math.sqrt((double)x); }
		double sqrt(long x) { return Math.sqrt((double)x); }
		double sqrt(double x) { return Math.sqrt(x); }
		double pow(double x, double y) { return Math.pow(x, y); }
		long pow(long x, long y) {
			if(y == 0) { return 1;
			}else {
				long tmp = pow(x, y / 2);
				return tmp * tmp * (y % 2 == 0 ? 1 : x);
			}
		}
		int gcd(int a, int b) { return b == 0 ? a : gcd(b, a % b); }
		long gcd(long a, long b) { return b == 0 ? a : gcd(b, a % b); }
		long lcm(long a, long b) { return a / gcd(a, b) * b; }
		int gcd(int[] array) {
			int gcd = 0;
			for(int i = 0; i < array.length; i ++) { gcd = gcd(gcd, array[i]); }
			return gcd;
		}
		long gcd(long[] array) {
			long gcd = 0;
			for(int i = 0; i < array.length; i ++) { gcd = gcd(gcd, array[i]); }
			return gcd;
		}

		int upperToInt(char a) { return a - 'A'; }
		int lowerToInt(char a) { return a - 'a'; }
		int numToInt(char a) { return a - '0'; }
		int charToInt(char a) { return a >= 'a' ? lowerToInt(a) : a >= 'A' ? upperToInt(a) : numToInt(a); }
		char intToUpper(int a) { return (char)(a + 'A'); }
		char intToLower(int a) { return (char)(a + 'a'); }
		char intToNum(int a) { return (char)(a + '0'); }
		int[] charToInt(char[] a) {
			int array[] = new int[a.length];
			for(int i = 0; i < a.length; i ++) { array[i] = charToInt(a[i]); }
			return array;
		}

		long[] div(long a) {
			List<Long> divList = new ArrayList<Long>();
			for(long i = 1; i * i <= a; i ++) {
				if(a % i == 0) {
					divList.add(i);
					if(i * i != a) { divList.add(a / i); };
				}
			}

			long div[] = new long[divList.size()];
			for(int i = 0; i < divList.size(); i ++) { div[i] = divList.get(i); }
			return div;
		}

		long[][] factor(long a) {
			List<Long> factorList = new ArrayList<Long>();
			List<Long> degreeList = new ArrayList<Long>();
			for(long i = 2; i * i <= a; i ++) {
				if(a % i == 0) {
					long count = 0;
					while(a % i == 0) {
						a /= i;
						count ++;
					}
					factorList.add(i);
					degreeList.add(count);
				}
			}
			if(a > 1) {
				factorList.add(a);
				degreeList.add(1L);
			}
			long factor[][] = new long[factorList.size()][2];
			for(int i = 0; i < factorList.size(); i ++) {
				factor[i][0] = factorList.get(i);
				factor[i][1] = degreeList.get(i);
			}
			Arrays.sort(factor, (sort1, sort2) -> Long.compare(sort1[0], sort2[0]));
			return factor;
		}

		boolean isPrime(long x) {
			boolean ok = x > 1;
			for(long i = 2; i * i <= x; i ++) {
				ok &= x % i != 0;
				if(!ok) return ok;
			}
			return ok;
		}
		boolean[] prime(int num) {
			boolean prime[] = new boolean[num];
			fill(prime, true);
			prime[0] = false;
			prime[1] = false;
			for(int i = 2; i < num; i ++) {
				if(prime[i]) {
					for(int j = 2; i * j < num; j ++) {
						prime[i * j] = false;
					}
				}
			}
			return prime;
		}

		long[][] countElements(long[] a, boolean sort) {
			int len = a.length;
			long array[] = new long[len];
			for(int i = 0; i < len; i ++) {
				array[i] = a[i];
			}
			if(sort) { Arrays.sort(array); }
			List<Long> elem = new ArrayList<Long>();
			List<Long> cnt = new ArrayList<Long>();
			long tmp = 1;
			for(int i = 1; i <= len; i ++) {
				if(i == len || array[i] != array[i - 1]) {
					elem.add(array[i - 1]);
					cnt.add(tmp);
					tmp = 1;
				}else {
					tmp ++;
				}
			}
			long counts[][] = new long[elem.size()][2];
			for(int i = 0; i < elem.size(); i ++) {
				counts[i][0] = elem.get(i);
				counts[i][1] = cnt.get(i);
			}
			return counts;
		}
		long[][] countElements(String str, boolean sort) {
			int len = str.length();
			char array[] = str.toCharArray();
			if(sort) { Arrays.sort(array); }
			List<Long> elem = new ArrayList<Long>();
			List<Long> cnt = new ArrayList<Long>();
			long tmp = 1;
			for(int i = 1; i <= len; i ++) {
				if(i == len || array[i] != array[i - 1]) {
					elem.add((long)array[i - 1]);
					cnt.add(tmp);
					tmp = 1;
				}else {
					tmp ++;
				}
			}
			long counts[][] = new long[elem.size()][2];
			for(int i = 0; i < elem.size(); i ++) {
				counts[i][0] = elem.get(i);
				counts[i][1] = cnt.get(i);
			}
			return counts;
		}

		int[] baseConvert(long x, int n) {
			long tmp = x;
			int len = 0;
			while(tmp > 0) { tmp /= n; len ++; }
			int digit[] = new int[len];
			int i = 0;
			tmp = x;
			while(tmp > 0) { digit[i ++] = (int)(tmp % n); tmp /= n; }
			return digit;
		}
		int[] baseConvert(int x, int n) {
			int tmp = x;
			int len = 0;
			while(tmp > 0) { tmp /= n; len ++; }
			int digit[] = new int[len];
			int i = 0;
			tmp = x;
			while(tmp > 0) { digit[i ++] = (int)(tmp % n); tmp /= n; }
			return digit;
		}

		int numDigits(long a) { return Long.toString(a).length(); }
		long bitFlag(int a) { return 1L << (long)a; }
		boolean isFlagged(long x, int a) { return (x & bitFlag(a)) != 0; }

		long countString(String str, String a) { return (str.length() - str.replace(a, "").length()) / a.length(); }
		long countStringAll(String str, String a) { return str.length() - str.replaceAll(a, "").length(); }

		int lowerBound(long[] array, long key) {
			return BS(array, key, true, true, true);
		}
		int lowerBound(long[] array, long key, int ng, int ok) {
			return BS(array, key, true, true, true, ng, ok);
		}
		int upperBound(long[] array, long key) {
			return BS(array, key, true, true, false);
		}
		int upperBound(long[] array, long key, int ng, int ok) {
			return BS(array, key, true, true, false, ng, ok);
		}
		int cntBS(long[] array, long key, boolean ascending, boolean greater, boolean equals) {
			return BS(array, key, ascending, greater, equals, true);
		}
		int cntBS(long[] array, long key, boolean ascending, boolean greater, boolean equals, int ng, int ok) {
			return BS(array, key, ascending, greater, equals, true, ng, ok);
		}
		int BS(long[] array, long key, boolean ascending, boolean greater, boolean equals) {
			return BS(array, key, ascending, greater, equals, false);
		}
		int BS(long[] array, long key, boolean ascending, boolean greater, boolean equals, int ng, int ok) {
			return BS(array, key, ascending, greater, equals, false, ng, ok);
		}
		int BS(long[] array, long key, boolean ascending, boolean greater, boolean equals, boolean count) {
			int ng = ascending ^ greater ? array.length : -1;
			int ok = ascending ^ greater ? -1 : array.length;
			return BS(array, key, ascending, greater, equals, count, ng, ok);
		}
		int BS(long[] array, long key, boolean ascending, boolean greater, boolean equals, boolean count, int ng, int ok) {
			int index = binarySearch(array, key, greater, equals, ng, ok);
			return count ? (int)abs(ok - index) : index;
		}
		int binarySearch(long[] array, long key, boolean greater, boolean equals, int ng, int ok) {
			while (abs(ok - ng) > 1) {
				int mid = (ok + ng) / 2;
				if(isOKforBinarySearch(array, mid, key, greater, equals)) {
					ok = mid;
				}else {
					ng = mid;
				}
			}
			return ok;
		}
		boolean isOKforBinarySearch(long[] array, int index, long key, boolean greater, boolean equals) {
			return (array[index] > key && greater)
				|| (array[index] < key && !greater)
				|| (array[index] == key && equals);
		}

		void reverse(String[] array) {
			String reversed[] = new String[array.length];
			for(int i = 0; i < array.length; i ++) { reversed[array.length - i - 1] = array[i]; }
			for(int i = 0; i < array.length; i ++) { array[i] = reversed[i]; }
		}
		void reverse(int[] array) {
			int reversed[] = new int[array.length];
			for(int i = 0; i < array.length; i ++) { reversed[array.length - i - 1] = array[i]; }
			for(int i = 0; i < array.length; i ++) { array[i] = reversed[i]; }
		}
		void reverse(long[] array) {
			long reversed[] = new long[array.length];
			for(int i = 0; i < array.length; i ++) { reversed[array.length - i - 1] = array[i]; }
			for(int i = 0; i < array.length; i ++) { array[i] = reversed[i]; }
		}
		void reverse(double[] array) {
			double reversed[] = new double[array.length];
			for(int i = 0; i < array.length; i ++) { reversed[array.length - i - 1] = array[i]; }
			for(int i = 0; i < array.length; i ++) { array[i] = reversed[i]; }
		}
		void reverse(boolean[] array) {
			boolean reversed[] = new boolean[array.length];
			for(int i = 0; i < array.length; i ++) { reversed[array.length - i - 1] = array[i]; }
			for(int i = 0; i < array.length; i ++) { array[i] = reversed[i]; }
		}
		void reverse(Object[] array) {
			Object reversed[] = new Object[array.length];
			for(int i = 0; i < array.length; i ++) { reversed[array.length - i - 1] = array[i]; }
			for(int i = 0; i < array.length; i ++) { array[i] = reversed[i]; }
		}
		void fill(int[] array, int x) { Arrays.fill(array, x); }
		void fill(long[] array, long x) { Arrays.fill(array, x); }
		void fill(double[] array, double x) { Arrays.fill(array, x); }
		void fill(boolean[] array, boolean x) { Arrays.fill(array, x); }
		void fill(int[][] array, int x) { for(int[] a : array) { fill(a, x); } }
		void fill(long[][] array, long x) { for(long[] a : array) { fill(a, x); } }
		void fill(double[][] array, double x) { for(double[] a : array) { fill(a, x); } }
		void fill(boolean[][] array, boolean x) { for(boolean[] a : array) { fill(a, x); } }
		void fill(int[][][] array, int x) { for(int[][] a : array) { fill(a, x); } }
		void fill(long[][][] array, long x) { for(long[][] a : array) { fill(a, x); } }
		void fill(double[][][] array, double x) { for(double[][] a : array) { fill(a, x); } }
		void fill(boolean[][][] array, boolean x) { for(boolean[][] a : array) { fill(a, x); } }

		void shuffleArray(int[] array){
			int n = array.length;
			Random rnd = new Random();
			for(int i = 0; i < n; i ++){
				int tmp = array[i];
				int randomPos = i + rnd.nextInt(n - i);
				array[i] = array[randomPos];
				array[randomPos] = tmp;
			}
		}
		void shuffleArray(long[] array){
			int n = array.length;
			Random rnd = new Random();
			for(int i = 0; i < n; i ++){
				long tmp = array[i];
				int randomPos = i + rnd.nextInt(n - i);
				array[i] = array[randomPos];
				array[randomPos] = tmp;
			}
		}
		void shuffleArray(double[] array){
			int n = array.length;
			Random rnd = new Random();
			for(int i = 0; i < n; i ++){
				double tmp = array[i];
				int randomPos = i + rnd.nextInt(n - i);
				array[i] = array[randomPos];
				array[randomPos] = tmp;
			}
		}

		void swap(int[] array, int i, int j) {
			int tmp = array[i];
			array[i] = array[j];
			array[j] = tmp;
		}
		void swap(long[] array, int i, int j) {
			long tmp = array[i];
			array[i] = array[j];
			array[j] = tmp;
		}
		void swap(double[] array, int i, int j) {
			double tmp = array[i];
			array[i] = array[j];
			array[j] = tmp;
		}

		long INF = (long)1e18 + 7;
		boolean isINF(long a) { return abs(a) > INF / 1000; }
		boolean isPlusINF(long a) { return a > 0 && isINF(a); }
		boolean isMinusINF(long a) { return isPlusINF(- a); }
		int I_INF = (int)1e9 + 7;
		boolean isINF(int a) { return abs(a) > I_INF / 1000; }
		boolean isPlusINF(int a) { return a > 0 && isINF(a); }
		boolean isMinusINF(int a) { return isPlusINF(- a); }


		// mods
		long MOD = (long)1e9 + 7; // 998244353;
		public long mod(long i) { i %= MOD; return i + (i < 0 ? MOD : 0); }

		long pow_m(long x, long y) {
			if(y == 0) { return 1;
			}else {
				long tmp = pow_m(x, y / 2);
				return mod(mod(tmp * tmp) * (y % 2 == 0 ? 1 : x));
			}
		}
		long[] pows_m(long x, int max) {
			long pow[] = new long[max + 1];
			pow[0] = 1;
			for(int i = 0; i < max; i ++) {
				pow[i + 1] = mod(pow[i] * x);
			}
			return pow;
		}

		int MAX_INV_SIZE = 100_100;
		HashMap<Long, Long> invMap = new HashMap<>();
		long inv(long x) {
			x = mod(x);
			if(invMap.containsKey(x)) { return invMap.get(x); }
			if(invMap.size() >= MAX_INV_SIZE) { return calInv(x); }
			invMap.put(x, calInv(x));
			return invMap.get(x);
		}
		long calInv(long x) { return pow_m(x, MOD - 2); }

		int MAX_FACT = 5_000_100;
		long fact[];
		long invFact[];
		boolean isFactPrepared = false;
		HashMap<Integer, long[]> factMap;
		void prepareFact() {
			fact = new long[MAX_FACT];
			Arrays.fill(fact, 0);
			invFact = new long[MAX_FACT];
			Arrays.fill(invFact, 0);
			fact[0] = 1;
			int maxIndex = min(MAX_FACT, (int)MOD);
			for(int i = 1; i < maxIndex; i ++) { fact[i] = mod(fact[i - 1] * i); }
			invFact[maxIndex - 1] = inv(fact[maxIndex - 1]);
			for(int i = maxIndex - 1; i > 0; i --) { invFact[i - 1] = mod(invFact[i] * i); }

			factMap = new HashMap<>();
			isFactPrepared = true;
		}

		long P(int n, int r) {
			if(!isFactPrepared) { prepareFact(); }
			if(n < 0 || r < 0 || n < r) { return 0; }
			if(n >= MAX_FACT) {
				if(!factMap.containsKey(n)) {
					long largeFact[] = new long[MAX_FACT];
					factMap.put(n, largeFact);
					fill(largeFact, -INF);
					largeFact[0] = 1;
				}
				long largeFact[] = factMap.get(n);
				int i = r;
				while(isINF(largeFact[i])) { i --; }
				for(; i < r; i ++) { largeFact[i + 1] = mod(largeFact[i] * (n - i)); }
				return largeFact[r];
			}
			return mod(fact[n] * invFact[n - r]);
		}
		long C(int n, int r) {
			if(!isFactPrepared) { prepareFact(); }
			if(n < 0 || r < 0 || n < r) { return 0; }
			return mod(P(n, r) * invFact[r]);
		}
		long H(int n, int r) { return C((n - 1) + r, r); }


		// grid
		class Grids {
			int h;
			int w;
			Grid[][] gs;
			Grids(int h, int w) {
				this.h = h;
				this.w = w;
				gs = new Grid[h][w];
				for(int i = 0; i < h; i ++) {
					for(int j = 0; j < w; j ++) {
						gs[i][j] = new Grid(i, j, h, w);
					}
				}
			}

			void init(boolean[][] b) {
				for(int i = 0; i < h; i ++) {
					for(int j = 0; j < w; j ++) {
						gs[i][j].b = b[i][j];
					}
				}
			}
			void init(long[][] val) {
				for(int i = 0; i < h; i ++) {
					for(int j = 0; j < w; j ++) {
						gs[i][j].val = val[i][j];
					}
				}
			}

			int dx[] = {0, -1, 1, 0, 0, -1, 1, -1, 1};
			int dy[] = {0, 0, 0, -1, 1, -1, -1, 1, 1};
			Grid next(Grid g, int i) {
				return isValid(g.x + dx[i], g.y + dy[i], g.h, g.w)
					? gs[g.x + dx[i]][g.y + dy[i]]
					: null;
			}
		}
		class Grid implements Comparable<Grid> {
			int x;
			int y;
			int h;
			int w;
			int i;
			boolean b;
			long val;

			Grid() {  }
			Grid(int x, int y, int h, int w) { init(x, y, h, w, false, 0); }
			Grid(int x, int y, int h, int w, boolean b) { init(x, y, h, w, b, 0); }
			Grid(int x, int y, int h, int w, long val) { init(x, y, h, w, false, val); }
			Grid(int x, int y, int h, int w, boolean b, long val) { init(x, y, h, w, b, val); }

			void init(int x, int y, int h, int w, boolean b, long val) {
				this.x = x;
				this.y = y;
				this.h = h;
				this.w = w;
				this.b = b;
				this.val = val;
				i = x * w + y;
			}

			@Override
			public int compareTo(Grid g) {
				return Long.compare(this.val, g.val);
			}
		}

		boolean isValid(int x, int y, int h, int w) {
			return x >= 0 && x < h && y >= 0 && y < w;
		}
		boolean isValid(Grid g) {
			return isValid(g.x, g.y, g.h, g.w);
		}

		// graph
		class Graph {
			int numNode;
			int numEdge;
			boolean directed;
			Edge edges[];
			Node nodes[];
			Node reversedNodes[];

			Graph(int numNode, int numEdge, boolean directed) {
				this.numNode = numNode;
				this.numEdge = numEdge;
				this.directed = directed;
				nodes = new Node[numNode];
				reversedNodes = new Node[numNode];
				for(int i = 0; i < numNode; i ++) {
					nodes[i] = new Node(i);
					reversedNodes[i] = new Node(i);
				}
			}

			void init(Edge[] edges) {
				this.edges = edges;
				for(Edge edge : edges) {
					nodes[edge.source].add(edge.target, edge.cost);
					if(directed) {
						reversedNodes[edge.target].add(edge.source, edge.cost);
					}else {
						nodes[edge.target].add(edge.source, edge.cost);
					}
				}
			}

			void clearNodes() {
				for(Node n : nodes) { n.clear(); }
				for(Node n : reversedNodes) { n.clear(); }
			}
		}

		class Node extends ArrayList<Edge> {
			int id;

			Node(int id) {
				this.id = id;
			}
			void add(int target, double cost) {
				add(new Edge(id, target, cost));
			}
		}

		class Edge implements Comparable<Edge> {
			int source;
			int target;
			double cost;
			Edge(int source, int target, double cost) {
				this.source = source;
				this.target = target;
				this.cost = cost;
			}

			@Override
			public int compareTo(Edge e) {
				return Double.compare(this.cost, e.cost);
			}
		}

public void solve() {
	long s[] = {ni(), ni(), 0};
	long t[] = {ni(), ni(), 0};
	int numNode = ni();
	long p2[][] = new long[numNode + 2][3];
	p2[0] = s;
	p2[1] = t;
	for(int i = 0; i < numNode; i ++) {
		p2[i + 2][0] = nl();
		p2[i + 2][1] = nl();
		p2[i + 2][2] = nl();
	}
	numNode += 2;
	int numEdge = numNode * (numNode - 1) / 2;
	Graph g = new Graph(numNode, numEdge, false);
	Edge edges[] = new Edge[numEdge];
	int index = 0;
	for(int i = 0; i < numNode; i ++) {
		for(int j = i + 1; j < numNode; j ++) {
			double dist = sqrt(pow(p2[i][0] - p2[j][0], 2) + pow(p2[i][1] - p2[j][1], 2));
			dist = max(0, dist - p2[i][2] - p2[j][2]);
			edges[index ++] = new Edge(i, j, dist);
		}
	}
	g.init(edges);

	double dist[] = dijkstra(g.nodes, 0);
	prtln(dist[1]);
}

int prev[];
double[] dijkstra(Node nodes[], int start) { // O((E+V)logV)
	double dist[] = new double[nodes.length];
	Arrays.fill(dist, INF);
	dist[start] = 0;

	prev = new int[nodes.length];

	Queue<Edge> q = new PriorityQueue<Edge>();
	q.add(new Edge(start, start, dist[start]));

	while(!q.isEmpty()) {
		Edge crt = q.poll();

		if(dist[crt.target] < crt.cost) { continue; }
		for(Edge e : nodes[crt.target]) {
			if(dist[e.target] > dist[e.source] + e.cost) {
				dist[e.target] = dist[e.source] + e.cost;
				q.add(new Edge(e.source, e.target, dist[e.target]));
				prev[e.target] = e.source;
			}
		}
	}

	return dist;
}

	}
}