program ex(f1,f2);
 type
  zn=array [0..12,0..12] of integer;
 var
  a:zn; f1,f2:text;
  i,j,k,m,n,l,p,s,ans,now:integer;
 procedure print(num:integer);
  begin
   if (num>0)and(num<ans) then ans:=num;
  end;
 procedure find(x,y,w:integer);
  var
   i,j,k,p:integer;
  begin
   if (x=m)and(y=n) then print(w)
    else
     begin
      if (x+1<=m) then find(x+1,y,w+a[x+1,y]);
      if (y+1<=n) then find(x,y+1,w+a[x,y+1]);
     end;
  end;


 begin
  assign(f1,'number.in'); reset(f1);
  assign(f2,'number.out'); rewrite(f2);
  readln(f1,m,n);
  for i:=1 to m do
   for j:=1 to n do read(f1,a[i,j]);
  ans:=9999;
  find(1,1,a[1,1]);
  if ans=9999 then writeln(f2,-1)
              else writeln(f2,ans);
  close(f1);
  close(f2);
 end.