#Japt, 16 12 bytes

@ZÔ¯V x}hVÆ1

Try it

@ZÔ¯V x}hVÆ1     :Implicit input of integers U=X & V=N
         VÆ1     :Map the range [0,V) returning 1 for each element
        h        :Push the result of the following to the array and repeat until its length equals U
@                :  Pass the array through the following function as Z
 ZÔ              :    Reverse Z
   ¯V            :    Slice to the Vth element
      x          :    Reduce by addition
       }         :  End function

Japt, 16 12 bytes

@ZÔ¯V x}hVÆ1

Try it

@ZÔ¯V x}hVÆ1     :Implicit input of integers U=X & V=N
         VÆ1     :Map the range [0,V) returning 1 for each element
        h        :Push the result of the following to the array and repeat until its length equals U
@                :  Pass the array through the following function as Z
 ZÔ              :    Reverse Z
   ¯V            :    Slice to the Vth element
      x          :    Reduce by addition
       }         :  End function

#Japt -h, 16 bytes

Æ1
Nrn ÆpUsNÎn)x

Try it

#Japt, 16 12 bytes

@ZÔ¯V x}hVÆ1

Try it

@ZÔ¯V x}hVÆ1     :Implicit input of integers U=X & V=N
         VÆ1     :Map the range [0,V) returning 1 for each element
        h        :Push the result of the following to the array and repeat until its length equals U
@                :  Pass the array through the following function as Z
 ZÔ              :    Reverse Z
   ¯V            :    Slice to the Vth element
      x          :    Reduce by addition
       }         :  End function