#include <bits/stdc++.h> #define int long long using namespace std; int a[1000005];//0为反面，1为正面 signed main(){ int n,m; cin >> n >> m; int b,c; for(int i=1;i<=m;i++){ cin >> b >> c; a[b]++; a[c+1]--; } int cnt=0; for(int i=1;i<=n;i++){ a[i]=abs(a[i]+a[i-1])%2; if(a[i]){ cnt++; } } cout << cnt; return 0; } //1 0 0 0 0 0 0 0 -1 0 //1 0 0 0 1 0 -1 0 -1 0 //2 0 0 0 1 0 -1 0 -1 -1 //2 0 1 0 1 0 -1 0 -2 -1 //2 1 1 0 1 0 -1 -1 -2 -1 //0 1 0 0 1 1 0 1 1 0