var n,i:integer;
Begin
read(n);
for i:= 2 to n-1 do
if n mod i = 0 then writeln('No');
End.
s:string;
read(s);
for i:= 1 to length(s) do
if s[i]="a" then n:=n+1;
writeln(n);
var n,i:integer;
Begin
read(n);
for i:= 2 to n-1 do
if n mod i = 0 then writeln('No');
End.
var n,i:integer;
s:string;
Begin
read(s);
for i:= 1 to length(s) do
if s[i]="a" then n:=n+1;
writeln(n);
End.