Submission #71673565

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Source Code Expand

#include<bits/stdc++.h>
#include<atcoder/all>
using namespace atcoder;
using namespace std;
using ll = long long;
using mint = modint998244353;
#define nl '\n'
#define rep(i, n) for(ll i = 0; i < (ll)(n); ++i)
template<typename T> bool chmin(T& a, T b){if(a > b){a = b; return true;} return false;}
template<typename T> bool chmax(T& a, T b){if(a < b){a = b; return true;} return false;}
const ll INF = (1LL << 62);
//--------------------------------------------------------------------------------
//--------------------------------------------------------------------------------

void solve()
{
    int n, m; cin >> n >> m;
    map<pair<ll,ll>, bool> mp;
    int ans = 0;
    rep(i, m)
    {
        ll r, c; cin >> r >> c;
        bool ok = true;
        for(int j = -1; j <= 1; ++j)
        {
            for(int k = -1; k <= 1; ++k)
            {
                if(mp[{r+j, c+k}]) ok = false;
            }
        }
        if(ok)
        {
            mp[{r, c}] = true;
            ans++;
        }
    }
    cout << ans << nl;
}
//--------------------------------------------------------------------------------

int main()
{
    cout << fixed << setprecision(10);
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    solve();
    return 0;
}

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