program light;
var f:array[0..8000000]of qword;
    t,k,m,n,i,j:longint;
    a,b,p:qword;
    r,s:real;
begin
assign(input,'light.in');
reset(input);
assign(output,'light.out');
rewrite(output);
readln(n);
repeat
  dec(n);
  readln(r,j);
  for t:=1 to j do
    begin
      a:=trunc(r*t);
      b:=a div 32;
      if a mod 32=0 then
        f[b]:=f[b] xor 1
      else f[b]:=f[b]xor(1 shl (a mod 32));
    end;
until n=0;
for t:=0 to 30 do
  p:=p+(1 shl t);
for i:=0 to 8000000 do
  if f[i]<>p then
    for j:=0 to 31 do
      if ((f[i] shr j)and 1)=1 then
        begin
          if j=0 then
            b:=i*32
          else b:=i*32+j;
          writeln(b);
          close(output);
          halt;
        end;
end.