Yup, VFIAX (the Vanguard S&P 500 index) is what everyone is saying.

Here's what you're invested in:

• VFIAX - S&P 500 fund; 500 biggest companies in the US
• VEIRX - basically a "value" tilt version of the S&P 500, but with far fewer companies (~200 vs 500)
• VSMGX - conservative, properly diversified fund - 60% in stocks (diversified with international stocks), 40% in bonds
• VUSXX - basically cash

So overall, here's what you're looking at (back of the napkin math):

• 35% - cash and bonds
• 55-60% - US stocks
• 5-10% - international stocks

So you're pretty lightweight on international stocks.

Personally, here's what I'd invest in:

• VITSX - Total US market, meaning there are smaller companies in there as well; 85% of it is the same as the S&P 500, so it's not that different, but small companies have historically done better than big companies, so it's good to have some of that exposure
• VTMGX - pretty much total international market

To be evenly diversified globally, you'd do something like 60% VITSX and 40% VTMGX, but I personally think the US will outperform, so I do 70% US and 30% international.

If you're risk-averse and feel like you'd sell if there's a market downturn, you can add some bonds (VBTLX) and put something like 10-20% in it (assuming you're young-ish; if you're over 50, increase it to 30-40%). But honestly, there's not much point if you'll just set it and forget it. If you want something super simple, VASGX looks pretty decent (20% bonds, so a bit less extreme fluctuations in a downturn).

A lot of people honestly just go 100% S&P 500, because a lot of those companies do business in other countries, so you're kind of getting international exposure. I personally prefer explicit international exposure though, hence my recommendation.