var m,n,j,s:longint;
function checkprime(x:longint):boolean;
var i:longint;
begin
for i:=2 to trunc(sqrt(x)) do if x mod i = 0 then exit(false) else exit(true);
end;
begin
write('Nhap m: '); readln(m);
write('Nhap n: '); readln(n);
for j:=m to n do
if checkprime(i) then s:=s+i;
write('S = ',s);
readln;
end.