ll exgcd(ll a, ll b, ll &x, ll &y) {
    if (b == 0) {
        x = 1, y = 0;
        return a;
    }
    ll xx, yy;
    ll g = exgcd(b, a % b, xx, yy);
    x = yy, y = xx - a / b * yy;
    return g;
}
void solve(){
    // 3x + 2y = 1
    ll x, y;
    ll g = exgcd(3, 2, x, y);
    cout << " g = " << g << " x = " << x << " y = " << y << '\n';
    // 期望 g = 1,且 3*x + 2*y = 1
}