求1~1500连续自然数的全部数字之和

编了个程序来解决

 1 var a,b,c,d,i,sum1,sum2,sum3,sum4:longint;
 2 begin
 3   sum1:=0;
 4   for i:=1 to 9 do inc(sum1,i);
 5   writeln(sum1);
 6   sum2:=0;
 7   for i:=10 to 99 do begin
 8     a:=i div 10;
 9     b:=i mod 10;
10     sum2:=sum2+a+b;
11   end;
12   writeln(sum2);
13   sum3:=0;
14   for i:=100 to 999 do begin
15     a:=i div 100;
16     b:=i div 10 mod 10;
17     c:=i mod 10;
18     sum3:=sum3+a+b+c;
19   end;
20   writeln(sum3);
21   sum4:=0;
22   for i:=1000 to 1500 do begin
23     a:=i div 1000;
24     b:=i div 100 mod 10;
25     c:=i div 10 mod 10;
26     d:=i mod 10;
27     sum4:=sum4+a+b+c+d;
28   end;
29   writeln(sum4);
30   writeln(sum1+sum2+sum3+sum4);
31 end.

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