#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const ll mod=(1LL<<31)-1;
const int N=2005;
int n,k;
ll X[N],Y[N];
void gen(){
    for(int i=1;i<=n;i++){
        if(i>1)X[i]=(Y[i-1]*233811181+1)%mod;
        Y[i]=(X[i]*233811181+1)%mod;
    }
}
const double pi=acos(-1.0);
const double eps=1e-8;
int sign(double x){
    if(fabs(x)<eps)return 0;
    return (x<0)?-1:1;
}
int dcmp(double x,double y){return sign(x-y);}
struct Point{
    double x,y;
    Point(double X=0,double Y=0):x(X),y(Y){}
    Point operator + (const Point &r) const{return Point(x+r.x,y+r.y);}
    Point operator - (const Point &r) const{return Point(x-r.x,y-r.y);}
    Point operator * (double p) const{return Point(x*p,y*p);}
    Point operator / (double p) const{return Point(x/p,y/p);}
};
double dot(Point A,Point B){return A.x*B.x+A.y*B.y;}
double length(Point A){return sqrt(dot(A,A));};
double dis(Point A,Point B){return length(A-B);}
double cross(Point A,Point B){return A.x*B.y-A.y*B.x;}
Point rotate(Point A,double rad){
    return Point(A.x*cos(rad)-A.y*sin(rad),A.x*sin(rad)+A.y*cos(rad));
}

struct Line{
    Point a,b;
    Point v;
    Line(){}
    Line(const Point &A,const Point &B,int op=0){
        if(!op){a=A,b=B,v=b-a;}
        else{a=A,v=B;b=a+v;}
    }
    Point point(double p){return a+v*p;}
};
Point line_line_inter(Line x,Line y){
    Point U=x.a-y.a;
    double t=cross(y.v,U)/cross(x.v,y.v);
    return x.a+x.v*t;
}

struct Circle{
    Point o;
    double r;
    Circle(){}
    Circle(const Point &O,double R):o(O),r(R){}
    bool inc(const Point &p){
        return dcmp(r,dis(o,p))>=0;
    }
};
Line get_line(Point a,Point b){return Line((a+b)/2,rotate(b-a,pi/2),1);}
Circle get_circle(Point a,Point b,Point c){
    Line u=get_line(a,b),v=get_line(a,c);
    Point o=line_line_inter(u,v);
    return Circle(o,dis(o,a));
}
Point p[N];
double R[N][N];
void min_circle(int l,int r){
    Circle c=Circle(p[l],0);
    for(int i=l;i<=r;i++){
        if(!c.inc(p[i])){
            c=Circle(p[i],0);
            for(int j=l;j<i;j++)
                if(!c.inc(p[j])){
                    c=Circle((p[i]+p[j])/2,dis(p[i],p[j])/2);
                    for(int k=l;k<j;k++)
                        if(!c.inc(p[k]))
                            c=get_circle(p[i],p[j],p[k]);
                }
        } 
        R[l][i]=c.r;
    }
}
vector<int>trans[N];
double f[N][N];
int main(){
    cin>>n>>k>>X[1];
    gen();
    for(int i=1;i<=n;i++)p[i]=Point(X[i],Y[i]);
    for(int i=1;i<=n;i++)min_circle(i,n);
    for(int i=1;i<=n;i++){
        for(int j=i;j;j--){
            if(R[j][i]!=R[j-1][i])
                trans[i].push_back(j);
        }
    }
    for(int i=1;i<=n;i++)
        for(int j=0;j<=k;j++)
            f[i][j]=1e16;
    for(int i=1;i<=n;i++)
        for(int j=1;j<=min(i,k);j++)
            for(auto o:trans[i]){
                f[i][j]=min(f[i][j],f[o-1][j-1]+R[o][i]);
           //     cout<<i<<" "<<j<<" "<<f[i][j]<<" "<<o-1<<" "<<j-1<<" "<<f[o-1][j-1]<<" "<<R[o][i]<<endl;
            }
    printf("%.10lf\n",f[n][k]);
    return 0;
}