#include <stdio.h>
#include <stdlib.h>

int main()
{ int n, m ,a,b,c=0,ans=0;
scanf("%d\n",&n);
long aa[200000] = {0};
scanf("%d\n",&m);
for(m>0;m>0;m--){
scanf("%d",&a);
scanf("%d",&b);
for(a>=0&&a<n&&b>0&&b<=n;a<=b;a++){
aa[a-1] = aa[a-1] + 1; }

}
for(c=0;c<=n-1;c++){ if(aa[c]%2==0) ans=ans+1; }

printf("\n");

printf("%d\n",ans);

return 0;
}