var nr,m,n,p,x,y,i:longint;
f,g:text;
begin
assign(f,'stergeri.in');reset(f);
assign(g,'stergeri.out');rewrite(g);
read(f,n,m,p);
for i:=1 to m do begin
read(f,x);
readln(f,y);
if x<p then
begin
p:=p+(y-x+1);
n:=n-(y-x+1);
end;
end;
if n<p then write(g,'0')
else write(g,p);
close(f);
close(g);
end.