imos.cpp

// BOJ 5541 釘 (Nails)

#include <bits/stdc++.h>
#define sz size()
#define bk back()
#define fi first
#define se second

using namespace std;
typedef long long ll;
typedef pair<int, int> pii;

int main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);

    int n, m;
    cin >> n >> m;

    vector<vector<int>> imos(n + 5, vector<int>(n + 5));
    while (m--) {
        int a, b, x;
        cin >> a >> b >> x;

        imos[a][b]++;
        imos[a][b + 1]--;
        imos[a + x + 1][b]--;
        imos[a + x + 2][b + 1]++;
        imos[a + x + 1][b + x + 2]++;
        imos[a + x + 2][b + x + 2]--;
    }

    for (int i = 1; i <= n; i++)
        for (int j = 1; j <= n; j++)
            imos[i][j] += imos[i][j - 1];

    for (int i = 1; i <= n; i++)
        for (int j = 1; j <= n; j++)
            imos[i][j] += imos[i - 1][j];

    for (int k = 2; k <= 2 * n; k++) {
        for (int i = max(1, k - n); i <= min(n, k - 1); i++) {
            int j = k - i;
            imos[i][j] += imos[i - 1][j - 1];
        }
    }

    int ans = 0;
    for (int i = 1; i <= n; i++)
        for (int j = 1; j <= n; j++)
            if (imos[i][j] > 0)
                ans++;

    cout << ans;
}