C++. ЛЕГКАЯ, помогите пж. Help me,please.

Question

Find the product of those numbers from a given rase whose number of units is a multiple of "m".
Найти произведение тех чисел из заданного диапазона, у которых число единиц кратно числу m
Please,say me about my mistake.
Пожалуйста,скажите где ошибка.

My trying:
https://code.sololearn.com/c76Fi6k0GDXF/?ref=app

Answer 1

What about the for loop without initialization like this:
for(;i<10;I++):

Answer 2

What is n, k values? Give a sample input and output?
What is output, if input is 5 1 20?

Answer 3

Please, give a code. I dont understand one sentence with code