算法模板——单个值欧拉函数

 1 var i:int64;
 2 function Eula(x:int64):int64;
 3          var res:int64;i:longint;
 4          begin
 5               res:=x;
 6               for i:=2 to trunc(sqrt(x)) do
 7                   begin
 8                        if (x mod i)=0 then
 9                           begin
10                                res:=(res div i)*(i-1);
11                                while (x mod i)=0 do x:=x div i;
12                           end;
13                   end;
14               if x>1 then res:=(res div x)*(x-1);
15               exit(res);
16          end;
17 begin
18      readln(i);writeln(Eula(i));
19      readln;
20 end.