import sys
import io, os
input = io.BytesIO(os.read(0,os.fstat(0).st_size)).readline

N,Q=map(int,input().split())

C=[[0,0],[0,1],[0,2],[0,3],[1,1],[1,2],[1,3],[2,2],[2,3],[3,3]]
AA=[(0, 0), (0, 1), (0, 2), (0, 3), (0, 4), (0, 5), (0, 6), (0, 7), (0, 8), (0, 9), (1, 4), (1, 5), (1, 6), (1, 7), (1, 8), (1, 9), (2, 7), (2, 8), (2, 9), (3, 9), (4, 4), (4, 5), (4, 6), (4, 7), (4, 8), (4, 9), (5, 7), (5, 8), (5, 9), (6, 9), (7, 7), (7, 8), (7, 9), (8, 9), (9, 9)]
AX=[[0, 0, 0, 0, 1, 1, 1, 1, 1, 1], [1, 0, 0, 0, 0, 0, 0, 1, 1, 1], [1, 1, 0, 0, 1, 0, 0, 0, 0, 1], [1, 1, 1, 0, 1, 1, 0, 1, 0, 0]]
LIST=[[-1]*4 for i in range(4)]

for i in range(len(C)):
    x,y=C[i]
    LIST[x][y]=i
    
def seg_function(x,y): # Segment treeで扱うfunction
    ANS=[1<<30]*10

    for i,j in AA:
        a,b=C[i]
        c,d=C[j]

        if b<=c:
            k=LIST[a][d]
            ANS[k]=min(ANS[k],x[i]+y[j])
    return ANS
                

seg_el=1<<(N.bit_length()) # Segment treeの台の要素数
SEG=[1<<30]*(10*(2*seg_el)) # 1-indexedなので、要素数2*seg_el.Segment treeの初期値で初期化

def update(n,x,seg_el): # A[n]をxへ更新
    i=n+seg_el
    SEG[i*10:i*10+10]=x
    i>>=1 # 子ノードへ
    
    while i!=0:
        SEG[i*10:i*10+10]=seg_function(SEG[i*2*10:i*2*10+10],SEG[(i*2+1)*10:(i*2+1)*10+10])
        i>>=1
        
def getvalues(l,r): # 区間[l,r)に関するseg_functionを調べる
    L=l+seg_el
    R=r+seg_el
    ANS1=[0]*10
    ANS2=[0]*10

    while L<R:
        if L & 1:
            ANS1=seg_function(ANS1, SEG[L*10:L*10+10])
            L+=1

        if R & 1:
            R-=1
            ANS2=seg_function(SEG[R*10:R*10+10], ANS2)
        L>>=1
        R>>=1

    return seg_function(ANS1, ANS2)

S=input().strip()

for i in range(N): # Aを対応する箇所へupdate
    SEG[(i+seg_el)*10:(i+seg_el)*10+10]=AX[S[i]-65]

for i in range(seg_el-1,0,-1): # 親の部分もupdate
    SEG[i*10:i*10+10]=seg_function(SEG[i*2*10:i*2*10+10],SEG[(i*2+1)*10:(i*2+1)*10+10])

LANS=[]
for tests in range(Q):
    x,y,z=input().split()

    if int(x)==1:
        y=int(y)-1

        update(y,AX[z[0]-65],seg_el)
    else:
        ANS=getvalues(int(y)-1,int(z))
        LANS.append(ANS[3])

print("\n".join(map(str,LANS)))