#include <iostream>
#include <iomanip>
#include <complex>
#include <vector>
#include <algorithm>
#include <cmath>
#include <array>
using namespace std;
const double EPS = 1e-8;
const double INF = 1e12;
const double PI = acos(-1);
#define EQ(n,m) (abs((n)-(m)) < EPS)
#define X real()
#define Y imag()

typedef complex<double> P;
typedef vector<P> VP;
struct L : array<P, 2>{
    L(const P& a, const P& b){ at(0)=a; at(1)=b; }
    L(){}
};
struct C{
    P p;
    double r;
    C(const P& p, const double& r) : p(p), r(r) {}
    C(){}
};

namespace std{
    bool operator < (const P& a, const P& b){
        return !EQ(a.X,b.X) ? a.X<b.X : a.Y+EPS<b.Y;
    }
    bool operator == (const P& a, const P& b){
        return abs(a-b) < EPS;
    }
}

double dot(P a, P b){
    return (conj(a)*b).X;
}
double cross(P a, P b){
    return (conj(a)*b).Y;
}
int ccw(P a, P b, P c){
    b -= a;
    c -= a;
    if(cross(b,c) > EPS) return +1; //ccw
    if(cross(b,c) < -EPS) return -1; //cw
    if(dot(b,c) < -EPS) return +2; //c-a-b
    if(abs(c)-abs(b) > EPS) return -2; //a-b-c
    return 0; //a-c-b
}
P unit(const P &p){
    return p/abs(p);
}
P rotate(const P &p, double rad){
    return p *P(cos(rad), sin(rad));
}

bool intersectSS(const L& a, const L& b){
    return ( ccw(a[0],a[1],b[0]) *ccw(a[0],a[1],b[1]) <= 0 ) &&
        ( ccw(b[0],b[1],a[0]) *ccw(b[0],b[1],a[1]) <= 0 );
}

P projection(const L& l, const P& p) {
    double t = dot(p-l[0], l[0]-l[1]) / norm(l[0]-l[1]);
    return l[0] + t*(l[0]-l[1]);
}
double distanceLP(const L &l, const P &p) {
    return abs(cross(l[1]-l[0], p-l[0])) /abs(l[1]-l[0]);
}
double distanceSP(const L &s, const P &p) {
    if(dot(s[1]-s[0], p-s[0]) < EPS) return abs(p-s[0]);
    if(dot(s[0]-s[1], p-s[1]) < EPS) return abs(p-s[1]);
    return distanceLP(s, p);
}

bool isParallel(const P &a, const P &b){
    return abs(cross(a,b)) < EPS;
}
bool isParallel(const L &a, const L &b){
    return isParallel(a[1]-a[0], b[1]-b[0]);
}

P crosspointLL(const L &l, const L &m) {
  double A = cross(l[1]-l[0], m[1]-m[0]);
  double B = cross(l[1]-l[0], l[1]-m[0]);
  return m[0] + B/A *(m[1]-m[0]);
}

VP crosspointCL(const C &c, const L &l){
    VP ret;
    P mid = projection(l, c.p);
    double d = distanceLP(l, c.p);
    if(EQ(d, c.r)){
        ret.push_back(mid);
    }else if(d < c.r){
        double len = sqrt(c.r*c.r -d*d);
        ret.push_back(mid +len*unit(l[1]-l[0]));
        ret.push_back(mid -len*unit(l[1]-l[0]));
    }
    return ret;
}
vector<L> getTangentLine(const C &c, const P &p){
    vector<L> ret;
    P dir = p -c.p;
    if(c.r < abs(dir) +EPS){
        P a = c.p + c.r*unit(dir);
        VP cp = crosspointCL(C(c.p, abs(dir)), L(a, a+dir*P(0,1)));
        for(int i=0; i<(int)cp.size(); i++){
            ret.push_back(L(p, c.p +c.r*unit(cp[i]-c.p)));
        }
    }
    return ret;
}

int main(){
    int n,d;
    cin >> n >> d;
    vector<C> c(n);
    for(int i=0; i<n; i++){
        double x,y,r;
        cin >> x >> y >> r;
        c[i] = C(P(x, y), r);
    }
    P s(25, 0), g(25, 94);

    vector<L> tangent;
    for(int i=0; i<n; i++){
        vector<L> ret = getTangentLine(c[i], s);
        tangent.insert(tangent.end(), ret.begin(), ret.end());
        ret = getTangentLine(c[i], g);
        tangent.insert(tangent.end(), ret.begin(), ret.end());
    }
    VP cand;
    cand.push_back((s+g)/2.0);
    for(int i=0; i<(int)tangent.size(); i++){
        for(int j=i+1; j<(int)tangent.size(); j++){
            if(!isParallel(tangent[i], tangent[j])){
                P cp = crosspointLL(tangent[i], tangent[j]);
                if(0 < cp.X +EPS && cp.X < 50 +EPS && 0 < cp.Y +EPS && cp.Y < 94 +EPS){
                    cand.push_back(cp);
                }
            }
        }
    }

    double ans = INF;
    for(int i=0; i<(int)cand.size(); i++){
        L e[2] = {L(s, cand[i]), L(g, cand[i])};
        int count = 0;
        for(int j=0; j<n; j++){
            if(abs(cand[i] -c[j].p) +EPS < c[j].r){
                count++;
                continue;
            }
            if(distanceSP(e[0], c[j].p) +EPS < c[j].r) count++;
            if(distanceSP(e[1], c[j].p) +EPS < c[j].r) count++;
        }
        if(count <= d){
            ans = min(ans, abs(e[0][1] -e[0][0]) +abs(e[1][1] -e[1][0]));
        }
    }
    if(ans == INF){
        cout << -1 << endl;
    }else{
        cout << fixed << setprecision(10);
        cout << ans << endl;
    }
    return 0;
}


Measured memory_bytes: 3360