program j303;
var a1:array[1..50] of integer;
var i,j,t,t2,n,n2:integer;
begin
n:=50;
for i:=1 to n do a1[i]:=0;
n2:=round(sqrt(n));
for i:=2 to n2 do
if (a1[i]=0) then
begin
t2:=n div i;
for j:=2 to t2 do a1[i*j]:=1;
end;
t:=0;
for i:=2 to n do
if (a1[i]=0) then
begin
write(i:4); inc(t);
if (t mod 10=0) then writeln;
end;
writeln;
end.
输出： 2 3 5 7 11 13 17 19 23
29 31 37 41 43 47