#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define ld long double
#define MP make_pair
const int MAXN=2005;
const ld dx=1e-18;
const int MOD=(1ll<<31)-1;
const ll P=233811181;
int n,k;ll x;
struct Point{ld x,y;}p[MAXN];
ld a[MAXN][MAXN],f[MAXN][MAXN];
ld dis(Point x,Point y){return sqrt((x.x-y.x)*(x.x-y.x)+(x.y-y.y)*(x.y-y.y));}
ll chg(ll &x){return x=(x*P+1)%MOD;}
struct Line{ld k,b;};// this line is kx+b.
Point operator *(Line n,Line m){
	ld x=(n.b-m.b+dx)/(m.k-n.k+dx);
	return (Point){x,n.k*x+n.b};
} 
Line plumbline(Point x,Point y){
	Point z=(Point){(x.x+y.x)/2,(x.y+y.y)/2};
	ld k=(y.y-x.y+dx)/(y.x-x.x+dx);
	return (Line){-1/k,z.y+z.x/k};
} 
Point circle(Point x,Point y,Point z){
	return plumbline(x,y)*plumbline(y,z);
}
Point o;ld r;
int main(){
	ios::sync_with_stdio(false);
	cin>>n>>k>>x;
	p[1].x=x;p[1].y=chg(x);
	for(int i=2;i<=n;i++) p[i].x=chg(x),p[i].y=chg(x);
	for(int t=1;t<=n;t++){
		Point o=(Point){0,0};ld r=0;
		for(int i=t;i<=n;i++){
			if(dis(p[i],o)>r){
				o=p[i];r=dis(p[i],o);
				for(int j=t;j<i;j++) if(dis(p[j],o)>r+dx){
					o=(Point){(p[j].x+p[i].x)/2,(p[j].y+p[i].y)/2};
					r=dis(p[i],o);
					for(int k=t;k<j;k++) if(dis(p[k],o)>r+dx){
						o=circle(p[i],p[j],p[k]);
						r=dis(p[i],o);
					}
				}
			}
			a[t][i]=r;
		}
	}
	for(int i=1;i<=n;i++) for(int j=0;j<=k;j++) f[i][j]=1e18;
	for(int i=1;i<=n;i++){
		for(int j=i;j>=1;j--) if(a[j][i]!=a[j-1][i]||j==1){
			for(int t=1;t<=k;t++) f[i][t]=min(f[i][t],f[j-1][t-1]+a[j][i]);
		}
	}
	cout<<setprecision(12)<<f[n][k]<<endl;
	return 0;
}