var

a,f:array[1..10000000] of longint;

b,i,j,n,s,x,y:longint;

begin

read(b,n);

for i:=1 to n do

a[i]:=0;

for i:=1 to n do

begin

readln(x,y);

a[x]:=1-a[x];

a[y+1]:=1-a[y+1];

end;

for i:=1 to b do

begin

if a[i]=1

then s:=s+1;

f[i]:=s mod 2;

end;

s:=0;

for i:=1 to b do

if f[i]=1

then s:=s+1;

writeln(s);

end.