#include<bits/stdc++.h>
using namespace std;
const int N=2010;
typedef long long ll;
typedef double db;
const int P=(1ll<<31)-1;
const db inf=1e100;

ll sqr(int x) { return 1ll*x*x; }
db dis(int x1,int y1,int x2,int y2) { return sqrtl(sqr(x2-x1)+sqr(y2-y1)); }
int f(int x) { return (1ll*x*233811181+1)%P; }

int n,k;
int x[N],y[N];
ll d[N][N];
ll calc[N][N];
db dp[N][N];

int main()
{
    scanf("%d%d%d",&n,&k,&x[1]);
    y[1]=f(x[1]);
    for(int i=2;i<=n;i++) x[i]=f(y[i-1]),y[i]=f(x[i]);
    for(int i=1;i<=n;i++) for(int j=i+1;j<=n;j++) d[i][j]=d[j][i]=sqr(x[i]-x[j])+sqr(y[i]-y[j]);
    for(int len=1;len<=n;len++) for(int l=1;l+len-1<=n;l++)
    {
        int r=l+len-1;
        calc[l][r]=max(max(calc[l][r-1],calc[l+1][r]),d[l][r]);
        // cerr<<l<<" "<<r<<" "<<calc[l][r]<<"\n";
    }

    for(int i=0;i<=n;i++) for(int j=0;j<=k;j++) dp[i][j]=inf;
    dp[0][0]=0;
    for(int i=1;i<=n;i++)
    {
        for(int j=i;j;j--) if(calc[j][i]!=calc[j-1][i])
        {
            for(int l=1;l<=k;l++) dp[i][l]=min(dp[i][l],dp[j-1][l-1]+sqrt(calc[j][i]));
        }
    }
    printf("%.20lf\n",dp[n][k]/2);
    return 0;
}