In Brazil, a country known for its fine leather footwear, the national shoe is actually the rubber flip-flop. Chinelos.

Never having been a huge flip-flop fan, I do nevertheless arrive unintentionally prepared with a pair of rubber flip-flops, in navy and white striped soles.

I buy my first new Brazilian pair at a newsstand on day 1 in Rio. White Ipanemas. They cost about $6 and I can’t help myself. I buy the same size as my striped pair, 37/38; but when I get back to the hotel and try them on, they’re enorme. Like barcos on my feet. Barges. Rubber baby buggy barges. Sneaky South American sizing looks just like Euro, but it’s not. One size has made a terrível diferença.

Oh well.

The next day, it’s nice in Rio and so we set out with our flip-flops on. After about an hour in my striped ones, Euro size 37/38, the straps start to rub and hurt. Really, I think, these simple, soft shoes are hurting my feet? I’ve never done city walking in them before, true, but they’re my normal size and should work. Other people seem perfectly bem in their flip-flops; in fact, these simple sandals — also known as thongs, zories, Jandals, flappers, slaps, slippers — seem like extensions of their feet. I take mine off at the praia and walk in the sand and play in the agua, and the abrasion is somewhat healed by the salt.

On the way back to the hotel, however, we happen to walk by this flip-flop store called Havaianas, which happens to be the brand of the things on my feet. A whole store of these? [There are stores all over the world, I find out later.] The shoe-lover in me trumps the flip-flop skeptic, and we go in.

Hundreds of styles of rubber flip-flops, and the store is packed. The salesman, a young guy who speaks a modicum of way too many línguas (English, Spanish, Italian, German, and Dutch) strikes up a conversação. “Where did you get those?” he asks, pointing at my feet. “USA,” I answer, and he fetches the current Brazilian version. “Well, let me know if you need help finding flip-flops in the right size.” The comment, though spoken in plain Inglês, goes right over my head.

I try on 7, maybe 8, styles. There are high-heeled flip-flops in this store, platform flip-flops, sparkly ones, athletic ones, and every conceivable permutation of pattern and color. I cannot make up my mind, but am very excited, at last, to leave with a smaller flip-flop in black and lime green, which, I only later find out, is really more of a man’s shoe. I like them, though — that is, until I’ve walked around half a day, in the rain this time, and find myself with an uglier version of the abrasion problem. We buy Band-aids (ataduras) and tape and, after a quick bench-sit, I look like a gymnast on vacation in an event-hosting country.

Day three, it is really raining in Rio. I mean torrential chuvas. There is no way we’re wearing our other shoes, so I slip on the stripes again with Band-aids and white tape. Mix it up. The mistério of this simple shoe not working for me has begun to drive me a little crazy (along with the sweet, strong Brazilian café) and I start studying people who seem perfectly content with their flip-flops on for hours and hours at a time. For lifetimes, probably. Because I’m tired and feel defeated, my head starts to droop, and by virtue of this drooping, my eyes lower, eventually to rest on all the feet going by, the feliz feet of people who know the secret to wearing flip-flops well. That’s when I notice it.

These people are all wearing flip-flops that seem way too small. Their toes sometimes hang a teeny bit over and their heels, too, or come just to the edge. Everyone wears them this way for one simple reason: this is proper flip-flop sizing.

I remember having eyed a pair of white Havaianas at a grocery store around the block from the hotel and drag my marido back into the fray for one more round. Size 34-35. White with a little Brazileiro flag on the strap. They look like a cross between a nurse’s flip-flop, a child’s shoe, and rest chinelos for Brazilian gymnasts in a foreign event-hosting country.

I slip one on like a glass slipper, and, then the other and bingo, instant fit. I know they’ll work, and they do. So I guess proverbs are true the world over, because in this case, as in many others, três é o charme!