What is the name of that kind of bread that foreigners love to eat, which is so hard that it requires a knife to cut hard?

Russian big bar.

Daliba is a staple food on the Russian table. At first glance, its color looks like Chinese sorghum noodles. It is cut into slices and tastes a little sour and salty. The yeast used in brown bread contains a variety of vitamins and biological enzymes, which is extremely nutritious and easy to digest. And the storage time is long.