#include<bits/stdc++.h>
using namespace std;
double R,eps=1e-10;
struct P{double x,y;}a[2005],O;
double dis(P x,P y){return sqrt((x.x-y.x)*(x.x-y.x)+(x.y-y.y)*(x.y-y.y));}
double pp[2005][2005];
P center(P x,P y,P z)
{
    double a1=y.x-x.x,b1=y.y-x.y,
            c1=(a1*a1+b1*b1)/2,a2=z.x-x.x,
            b2=z.y-x.y,c2=(a2*a2+b2*b2)/2,
            d=a1*b2-a2*b1;
    return (P){x.x+(c1*b2-c2*b1)/d,x.y+(a1*c2-a2*c1)/d};
}
double cal(int n,P *b,int st){
    int i,j,k;
    for(i=0;i<n;i++)a[i]=b[i];
//    for(i=0;i<n;i++)swap(a[rand()%n],a[i]);
    for(O=a[0],R=0,i=1;i<n;i++) {
        if (dis(a[i], O) > R + eps)
            for (O = a[i], R = 0, j = 0; j < i; ++j)
                if (dis(a[j], O) > R + eps) {
                    O = (P) {(a[i].x + a[j].x) / 2, (a[i].y + a[j].y) / 2}, R = dis(O, a[i]);
                    for (k = 0; k < j; k++)if (dis(a[k], O) > R + eps)O = center(a[k], a[j], a[i]), R = dis(O, a[i]);
                }
        pp[st][st+i+1]=R;
    }
    return R;
}
P dot[2005];
double dp[2005][2005];
int n,k;

long long x[2005],y[2005];
long long nxt(long long x){
    return (x*233811181ll+1)%((1ll<<31)-1);
}

int main(){
    srand(time(0));
    scanf("%d%d%lld",&n,&k,&x[1]);
    if (k>=n){
        printf("0.0\n");
        return 0;
    }
    y[1]=nxt(x[1]);
    for (int i=2;i<=n;i++) {
        x[i] = nxt(y[i - 1]);
        y[i] = nxt(x[i]);
    }
    for (int i=0;i<n;i++) dot[i]={x[i+1],y[i+1]};

    double final_res = 1e30;
    if (1ll*n*n*min(k,n-k)>=100000000) {
        for (int i = 0; i + n - k + 1 - 1 < n; i++) {
            double r = cal(n - k + 1, dot + i, i);
            final_res = min(r, final_res);
        }
    } else{
        for (int i=0;i<=n;i++)
            for (int j=0;j<=k;j++) dp[i][j]=1e30;
        dp[0][0]=0;
        for (int i=0;i<n;i++) cal(n-i,dot+i,i);
        for (int i=0;i<=n;i++)
            for (int j=max(k-n+i,0);j<=min(i,k);j++)
                for (int l=i+1;l<=n;l++) dp[l][j+1]=min(dp[l][j+1],dp[i][j]+pp[i][l]);
        final_res=dp[n][k];
    }
//     1319350480.8007326126
    printf("%.10f\n",final_res);
}