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.toString(), i);

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

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