program medic;
type
shuzu=array[1..2000,1..2] of integer;
shuzu1=array[0..200,0..200]of integer;
var
i,j,m,n,a,t:integer;
b:shuzu1;
f1,f2:text;
flag:boolean;
s:shuzu;
function max(x,y:longint):longint;
begin
if x>y then max:=x
else max:=y;
end;
begin
assign(f1,'medic.in');reset(f1);
assign(f2,'medic.out');rewrite(f2);
readln(f1,t,m);
fillchar(b,sizeof(b),0);
for i:=1 to m do
  readln(f1,s[i,1],s[i,2]);
for i:=1 to m do
   for j:=1 to t do
    if j<s[i,1] then
     b[i,j]:=b[i-1,j]
    else b[i,j]:=max(b[i-1,j],b[i-1,j-s[i,1]]+s[i,2]);
writeln(f2,b[m,t]);
      close(f2);
      end.