var a,b:array[1..1000000] of integer;
i,c,n,k,m,l:integer;
d:int64;
begin
l:=1;
d:=0;
readln(n);
c:=1;
for i:=1 to n-1 do
c:=c*10;
for i:=1 to n do begin
read(a[i],b[i]);
readln;
end;
for i:=1 to n do begin
k:=a[i]+b[i];
m:=(c*a[i]+c*b[i]);
d:=d+(c*a[i]+c*b[i]);
if m>k then
c:=m div(k*10);
end;
writeln(d);
readln
end.

integer doesn't take so much