Об­ра­зуй­те от слова DIFFICULT од­но­ко­рен­ное слово так, чтобы оно грам­ма­ти­че­ски и лек­си­че­ски со­от­вет­ство­ва­ло со­дер­жа­нию тек­ста.

Most of us probably feel we need around eight hours sleep to function well. Some people have ______ in getting enough sleep and this may lead to serious health problems.