uses crt;
var m,n,i,j,a,s,max:integer;
v:array[1..30000]of integer;k,p:array[1..300]of integer;
label 1;
begin
max:=0;
read(n,m);
For i:=1 to n do begin
read(v[i]);
If v[i]>max then max:=v[i];
end;
For i:=1 to m do read(k[i],p[i]);
For i:=1 to n do begin
For j:=i+1 to n do begin
If v[i]<v[j] then begin
a:=v[j];
v[j]:=v[i];
v[i]:=a;
end;
end;
end;
For i:=1 to m do begin
a:=0;s:=0;
For j:=1 to m do begin
a:=a+1;
s:=s+v[j];
If (a=k[i])and (s mod p[i]=0) then goto 1
else If (a=k[i]) and (s mod p[i]>0) then begin
a:=a-1;
s:=s-v[j];
end;
end;
If s>0 then begin
1:If s mod p[i]=0 then write(s)
else write('-1');
end
else write('-1');
writeln;
end;
readln;
end.