function test(str, count)
{
    var repeated = str.repeat(count);
    // Expand the rope.
    return repeated[0] + repeated[count >> 1] + repeated[repeated.length - 1];
}

// General cases.
for (var i = 0; i < 1000; ++i)
    test('  ', i);

// Small cases.
for (var i = 0; i < 1e4; ++i)
    test('  ', 5);

// Large cases.
for (var i = 0; i < 100; ++i)
    test('  ', 10000);