14
99 98 97 96 95 94 02 91 
79 78 00 76 75 74 73 72
69 68 67 66 65 64 63 62 
49 48 47 46 04 44 43 42 
39 38 37 36 35 34 33 32
29 28 27 26 25 24 23 22
19 18 04 13 12 11 10 09
09 08 07 04 03 02 01 00
我的 63.832
正解 57.401
var
ans:extended;
used:int64;
yy,n,i,j,k,l,xx:longint;
dp:array[1..8,1..8,1..8,1..8,1..15] of int64;
p:array[1..8,1..8] of int64;
sum:array[1..8,1..8,1..8,1..8] of int64;
function min(a,b:longint):longint;
begin
if a<b then exit(a) else exit(b);
end;
function find(x1,y1,x2,y2,fen:longint):longint;
var
i,temp:longint;
begin
//if x2-x1+y2-y1<fen then exit(100000000);
if dp[x1,y1,x2,y2,fen]<>maxlongint then exit(dp[x1,y1,x2,y2,fen]);
if fen=1 then
 begin
 dp[x1,y1,x2,y2,1]:=sum[x1,y1,x2,y2]*sum[x1,y1,x2,y2];
 exit(dp[x1,y1,x2,y2,1]);
 end;
temp:=maxlongint;
for i:=x1 to x2-1 do
if y2-y1+i-x1>=fen-1 then
temp:=min(temp,find(x1,y1,i,y2,fen-1)+sum[i+1,y1,x2,y2]*sum[i+1,y1,x2,y2]);
for i:=x1+1 to x2 do
if y2-y1+x2-i>=fen-1 then
temp:=min(temp,find(i,y1,x2,y2,fen-1)+sum[x1,y1,i-1,y2]*sum[x1,y1,i-1,y2]);
for i:=y1 to y2-1 do
if x2-x1+i-y1>=fen-1 then
temp:=min(temp,find(x1,y1,x2,i,fen-1)+sum[x1,i+1,x2,y2]*sum[x1,i+1,x2,y2]);
for i:=y1+1 to y2 do
if x2-x1+y2-i>=fen-1 then
temp:=min(temp,find(x1,i,x2,y2,fen-1)+sum[x1,y1,x2,i-1]*sum[x1,y1,x2,i-1]);
dp[x1,y1,x2,y2,fen]:=temp;
exit(dp[x1,y1,x2,y2,fen]);
end;
begin
fillchar(sum,sizeof(sum),0);
readln(n);
for i:=1 to 8 do
for j:=1 to 8 do
read(p[i,j]);
for i:=1 to 8 do
for j:=1 to 8 do
for k:=i to 8 do
for l:=j to 8 do
for xx:=i to k do
for yy:=j to l do
sum[i,j,k,l]:=sum[i,j,k,l]+p[xx,yy];
for i:=1 to 8 do
for j:=1 to 8 do
for k:=i to 8 do
for l:=j to 8 do
for xx:=1 to n do
dp[i,j,k,l,xx]:=maxlongint;
used:=find(1,1,8,8,n);
//writeln(used);
ans:=sqrt((-1*sum[1,1,8,8]*sum[1,1,8,8]/n+used)/n);
writeln(ans:0:3);
end.