#include <cstdio>
#include <cmath>
#include <cstring>
#include <algorithm>
using namespace std;
int n;
int sum;
int dp[16][9][9][9][9];
int g[9][9][9][9];
int mp[9][9];
double ave;
void init(){
sum=0;
scanf("%d",&n);
for(int i=0;i<8;i++){
for(int j=0;j<8;j++){
scanf("%d",&mp[i][j]);
sum+=mp[i][j];
}
}
ave = sum*1.0/n;
for(int x=0;x<9;x++)
for(int y=0;y<9;y++){
for(int xx=x;xx<9;xx++)
for(int yy=y;yy<9;yy++){
int ans=0;
for(int i=x;i<=xx;i++)
for(int j=y;j<=yy;j++){
ans+=mp[i][j];
}
g[x][y][xx][yy]=ans*ans;
}
}
}
int DP(int k,int x,int y,int xx,int yy)
{
int i,ans=0;
if(dp[k][x][y][xx][yy]>=0) return dp[k][x][y][xx][yy];
if(k==n⑴) return g[x][y][xx][yy];
dp[k][x][y][xx][yy]=1<<29;
for(i=x;i<xx;i++){
ans=min(DP(k+1,x,y,i,yy)+g[i+1][y][xx][yy],DP(k+1,i+1,y,xx,yy)+g[x][y][i][yy]);
dp[k][x][y][xx][yy]=min(ans,dp[k][x][y][xx][yy]);
}
for(i=y;i<yy;i++){
ans=min(DP(k+1,x,y,xx,i)+g[x][i+1][xx][yy],DP(k+1,x,i+1,xx,yy)+g[x][y][xx][i]);
dp[k][x][y][xx][yy]=min(ans,dp[k][x][y][xx][yy]);
}
return dp[k][x][y][xx][yy];
}
int main(){
init();
memset(dp,⑴,sizeof(dp));
DP(0,0,0,7,7);
printf("%.3f
",sqrt((dp[0][0][0][7][7])*1.0/n-ave*ave));
return 0;
}
#include<iostream>
#include<cmath>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<algorithm>
using namespace std;
int n;
long double d[16][9][9][9][9];
long double s[9][9][9][9];
double map[9][9];
int count_map[9][9];
long double sum;
long double ave;
const int m = 8;
const double INF = 0x7f7f7f7f;
double count(int i,int j,int i2,int j2)
{
double ans = count_map[i2][j2] - count_map[i2][j⑴] - count_map[i⑴][j2] + count_map[i⑴][j⑴];
return ans*ans;
}
void init()
{
int i,j;
sum = 0;
memset(count_map,0,sizeof(count_map));
for(i=1;i<=8;i++)
{
for(j=1;j<=8;j++)
{
scanf("%lf",&map[i][j]);
sum+=map[i][j];
count_map[i][j] = count_map[i][j⑴] +
count_map[i⑴][j] -
count_map[i⑴][j⑴] +
map[i][j];
}
}
ave = sum*1.0/n;
int i2,j2;
for(i=1;i<=m;i++)
{
for(j=1;j<=m;j++)
{
for(i2=i;i2<=m;i2++)
{
for(j2 = j;j2<=m;j2++)
{
s[i][j][i2][j2] = count(i,j,i2,j2);
d[0][i][j][i2][j2] = s[i][j][i2][j2];
}
}
}
}
}
void dp()
{
int k,i,j,i2,j2;
for(k=1;k<n;k++)
{
for(i=1;i<=m;i++)
{
for(j=1;j<=m;j++)
{
for(i2=i;i2<=m;i2++)
{
for(j2 = j;j2<=m;j2++)
{
d[k][i][j][i2][j2] = INF;
int t;
for( t = i;t<i2;t++)
d[k][i][j][i2][j2] = min(d[k][i][j][i2][j2],
min(d[k⑴][i][j][t][j2] + s[t+1][j][i2][j2],
s[i][j][t][j2] + d[k⑴][t+1][j][i2][j2]));
for( t = j;t<j2;t++)
d[k][i][j][i2][j2] = min(d[k][i][j][i2][j2],
min(d[k⑴][i][j][i2][t] + s[i][t+1][i2][j2],
s[i][j][i2][t] + d[k⑴][i][t+1][i2][j2]));
}
}
}
}
}
}
int main()
{
while(scanf("%d",&n) != EOF)
{
init();
dp();
long double ans = d[n⑴][1][1][m][m]*1.0/n - ave*ave;
printf("%.3f
",(double)sqrt(ans));
}
return 0;
}