var
x,i,s,f:integer;
begin
for x:=0 to 20 do
begin
s:=sqr(x)+x+49;
for i:=2 to s-1 do
if s mod i=0 then f:=1;
end;
if f=0 then writeln('yes')else writeln('no');
readln;
end.
var
x,i,s,f:integer;
begin
for x:=0 to 20 do
begin
s:=sqr(x)+x+49;
for i:=2 to s-1 do
if s mod i=0 then f:=1;
end;
if f=0 then writeln('yes')else writeln('no');
readln;
end.