Nearest smaller value

#include <bits/stdc++.h>

using namespace std;

long long N, x;
vector < int > a, v;

int main () {
  cin >> N;
  a = v = vector < int > (N + 1);
  for (int i = 0; i < N; i ++) {
    cin >> a[i];
    v[i] = i - 1;
    cout << v[i] << ' ';
    while (~v[i] && a[v[i]] >= a[i])
      v[i] = v[v[i]], cout << v[i] << ' ';
    cout << '\n';
  }
  return 0;
}
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