program xmz;
var
f1,f2:text;
w,ws:array[0..1000]of longint;
t,l,n,a,b,c:longint;
s:array[0..1000]of real;
f:array[0..1000,0..1000]of real;
begin
 assign(f1,'convoy.in');assign(f2,'convoy.out');
 reset(f1);rewrite(f2);
  read(f1,t,l,n);
 for a:=1 to n do
  begin
  read(f1,w[a],s[a]);
  s[a]:=(l/s[a])*60;
  ws[a]:=w[a]+ws[a-1];
  end;
 for a:=1 to n do
  for b:=1 to n-a+1 do
    if ws[b+a-1]-ws[b-1]<=t then
    begin
    for c:=b to b+a-1 do
      if f[a,b]<s[c] then f[a,b]:=s[c];
    end
   else
   for c:=1 to a-1 do
    if (f[a,b]>f[c,b]+f[a-c,b+c])or(f[a,b]=0) then
    f[a,b]:=f[c,b]+f[a-c,b+c];
  write(f2,f[n,1]:0:1);
close(f1);close(f2);
end.