N4 30 из 100

#include <iostream>
#include <cmath>
#include <vector>
#include <queue>
#include <algorithm>
#include <string>
#include <stack>
#include <set>
#include <map>
#define pii pair <int, int>
#define pb(x) push_back(x)
using namespace std;
using ll = long long;
using ld = long double;
using db = double;
void cv(vector <int> &v) {
    for (auto x : v) cout << x << ' ';
    cout << "\n";
}

void cvl(vector <ll> &v) {
    for (auto x : v) cout << x << ' ';
    cout << "\n";
}


void cvv(vector <vector <int> > &v) {
    for (auto x : v) cv(x);
    cout << "\n";
}

void cvb(vector <bool> v) {
    for (bool x : v) cout << x << ' ';
    cout << "\n";
}

void cvs(vector <string>  v) {
    for (auto a : v) {
        cout << a << "\n";
    }
}

void cvp(vector <pii> a) {
    for (auto p : a) {
        cout << p.first << ' ' << p.second << "\n";
    }
    cout << "\n";
}

ll S(ll a1, ll n) {
    return (2 * a1 + n - 1) * n / 2;
}

ll n, m;

ll frx, tox, fry, toy;

bool ok(int i, int j) {
    return i >= frx && i <= tox && j >= fry && j <= toy;
}
vector <int> dx = {1, 0, -1, 0}, dy = {0, 1, 0, -1};

bool sh = 0;
int main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    cin >> n >> m;
    frx = -2;
    tox = n - 1;
    fry = 0;
    toy = m - 1;
    ll cnt = 1;
    vector <vector <int> > a(n, vector <int> (m, 0));
    if (min(n, m) == 1) {
        cout << n * m;
        exit(0);
    }
    a[0][0] = 1;
    int i = 0, j = 0, to = 0;
    while (1) {
        //cnt +=
        while ( ok(i + dx[to], j + dy[to]) ) {
            i += dx[to];
            j += dy[to];
            a[i][j] = 1;
            cnt++;
        }
        if (sh) {
            cout << "to = " << to << "\n";
            cout << "frx tox = " << frx << ' ' << tox << "\n";
            cout << "fry toy = " << fry << ' ' << toy << "\n";
        }
        if (to == 0) {
            frx += 2;
            //tox -= 2;
        }
        else if (to == 2) {
            tox -= 2;
        }
        else if (to == 1) {
            fry += 2;
        }
        else if (to == 3) {
            toy -= 2;
        }
        to++;
        to %= 4;
        if (sh) {
            cout << "to = " << to << "\n";
            cout << "i + dx[to] j + dy[to] = " << i + dx[to] << ' ' << j + dy[to] << "\n";
        }
        if (!ok(i + dx[to], j + dy[to])) {
            break;
        }
    }
    if (sh) {
        cout << "i j = " << i << ' ' << j << "\n";
        cout << "to = " << to << "\n";
        cout << "ans\n";
    }
    cout << cnt << "\n";
    if (sh) {
        cvv(a);
    }
}