#include "bits/stdc++.h"
using namespace std;
#define ff first
#define ss second
#define pp pop_back
#define ll long long
#define pb push_back
#define pq priority_queue
#define ls(v) (int)v.size()
#define all(v) v.begin(),v.end()
#define rall(v) v.rbegin(),v.rend()
#define wr cout << "------------------------" << endl
#define tt debug
signed main(){
#ifdef parad0x
freopen("file.in","r",stdin);
#endif
#define print(...) 42
ios::sync_with_stdio(false);cin.tie(nullptr);
int n,k;
cin >> n >> k;
vector<int>v;
int m = 1;
v.pb(n);
for(int i = 1;i<=k;++i){
int idx,l;
cin >> idx >> l;
vector<int>a;
for(int j = 0;j<m;++j){
if(j == idx - 1){
a.pb(l);
a.pb(v[j] - l);
}
else{
a.pb(v[j]);
}
}
v = a;
m += 1;
}
sort(all(v));
v.erase(unique(all(v)),v.end());
cout << ls(v) << endl;
return 0;
}
