#!/bin/ruby
nums =Hash.new(0)
v=('a'..'z').to_a
(0..26).each{|i|
    nums[v[i]]=i
    }

def findp(s,len)
   count = 0

(0..len-1).each do |i|
  (i..len-1).each do |j|
    temp = s[i..j]
    count = count + 1 if temp == temp.reverse
  end
end
return count
    
end

def nuewFind(s,len)
    count=0
    vol=Hash.new(0)
    (s.split('')).each{|i|
        vol[i]=vol[i]+1
        count=count+1
        }
    diff=0
    vol.each{|k,v|
        if v!=0
            diff=diff+1
        end
        }
    
    vol.each{|k,v|
        if v==2
            count=count+diff
        end
        }
        return count
end



n,q = gets.strip.split(' ')
n = n.to_i
q = q.to_i
s = gets.strip

(0...q).each{|i|
    l= gets.strip.split(' ').map(&:to_i)
    if l.length==3
        puts nuewFind(s[l[1]..l[2]],l[2]-l[1]+1)
    else
        (l[1]..l[2]).each{|j|
            s[j]=v[(nums[s[j]]+l[3])%26]
            }
    end
    }