n,k=gets.split.map(&:to_i)
s=gets.chomp

cost=0
prize=0
b=->c{
  prize>0?(prize-=1):(cost+=1)
  c>?0&&prize+=c.to_i
}
if n<k
  s.each_char(&b)
  cost+=((k-1)/n-1)*[cost-prize,0].max
end
s[0,(k-1)%n+1].each_char(&b)
p cost