void triangle(int lignes) 
{

  for (int i=0; i<lignes; i++) {

    for (int j=lignes; j>i; j--)

      cout << " ";

    cout << "/";

    if (i < lignes - 1)

      for (int j=0; j<i*2; j++)

        cout << " ";

    else

      for (int j=0; j<i*2; j++)

        cout << "_";

    cout << "\\" << endl;

  }

}