program z1001;
var a:array[1..1000000] of int64;
    i,j:longint;
begin
i:=1;
while not seekeof do begin read(a[i]); i:=i+1; end;
for j:=i downto 1 do writeln(sqrt(a[j]):0:4);
end.

I have WA#1 and don't understand why

program z1001;
var a:array[1..1000000] of int64;
    i,j:longint;
begin
i:=1;
while not seekeof do begin read(a[i]); i:=i+1; end;

AHTUNG you missed here - i:=i-1; that;s all=)

for j:=i downto 1 do writeln(sqrt(a[j]):0:4);
end.