var  
 f:array[0..2000,0..2000] of longint;  
 a,b:array[0..2000] of longint;  
 n,m,i,j,k,l:longint;  
function min(x,y:longint):longint;  
begin  
 if x<y then exit(x);  
 exit(y);  
end;  
begin  
 readln(n,m);  
 for i:=1 to n do read(a[n-i+1]);  
 for i:=1 to m do read(b[m-i+1]);  
 for i:=1 to n do dec(a[i]);  
 for i:=1 to m do dec(b[i]);  
 fillchar(f,sizeof(f),120);  
 f[0,0]:=0;  
 for i:=1 to n do begin  
  for j:=1 to m do begin  
   f[i,j]:=min(f[i-1,j-1],min(f[i-1,j],f[i,j-1]))+a[i]*b[j];  
  end;  
 end;  
 writeln(f[n,m]);  
end.  

这是AC的代码

var
  f:array[1..2001,1..2001]of longint;
  a,b:array[1..1000]of longint;
  i,j,m,n,k:longint;
function min(x,y:longint):longint;
begin
  if x<y then exit(x);
  exit(y);
end;
begin
  readln(n,m);
  for i:=1 to n do
    begin
      read(a[i]);
      a[i]:=a[i]-1;
    end;
  for i:=1 to m do
    begin
      read(b[i]);
      b[i]:=b[i]-1;
    end;
  for i:=1 to n+1 do
    begin
      f[i,m]:=maxlongint;
      f[i,m+1]:=maxlongint;
    end;
  for j:=1 to m+1 do
    begin
      f[n,j]:=maxlongint;
      f[n+1,j]:=maxlongint;
    end;
  f[n+1,m+1]:=0;
  for i:=n downto 1 do
    for j:=m downto 1 do
      f[i,j]:=min(f[i,j],min(f[i+1,j+1],f[i+1,j]))+a[i]*b[j];
  writeln(f[1,1]);
end.

这是我63分的代码，但是我的超时了，为什么 题号是P1846