#include <bits/stdc++.h>
using namespace std;

int main(){
	
	long long L,N;
	cin>>L>>N;

	set<long long> S1[2];
	set<long long> S2[2];
	long long x,y;
	for(long long i=0;i<N;i++){
		cin>>x>>y;
		x--,y--;
		S1[abs((y-x))%2].insert(y-x);
		S2[(x+y)%2].insert(x+y);
	}
	vector<long long> V[2];
	long long ans = 0;
	for(long long i=0;i<2;i++){
		for(auto a:S1[i]){
			ans+=(long long)L-abs(a);
			V[i].push_back(a);
		}
		for(auto a:S2[i]){
			long long x = L-abs((L-1)-a);
			ans+=(long long)x;
			ans-=upper_bound(V[i].begin(),V[i].end(),x-1)-lower_bound(V[i].begin(),V[i].end(),-(x-1));
		}
	}
	cout<<ans<<endl;
	
	return 0;
}