Buggy python submission (verdict: Runtime Error):
L,A,B,M=map(int,input().split())
mod=M
C=A+B*(L-1)
ans=0
def S(x,l,r,mod):
    return ((pow(x,r+1)-pow(x,l))//(x-1))%mod
def Sa(x,l,r,mod):
    return (pow(x,r+1)-pow(x,l))//(x-1)
def SS(x,l,r,mod):
    if l==r:
        return x
    return ((r*pow(x,r+1)-l*pow(x,l)-Sa(x,l+1,r,mod))//(x-1))%mod
now=0
Sx=1
while True:
    if C<A:
        break
    if len(str(C))==1:
        r=C//B
    else:
        r=(C-pow(10,len(str(C))-1))//B
    if r==0:
        ans=(ans+C*Sx)%mod
        Sx=Sx*pow(10,len(str(C)),mod)%mod
        C-=B
        now+=1
    else:
        if now+r>=L:
            r=L-now-1
        x=pow(10,len(str(C)),mod)
        y0=(C*(S(x,1,r,mod)+1))%mod
        y1=(-1*B*SS(x,1,r,mod))%mod
        y=(Sx*(y0+y1))%mod
        ans=(ans+y)%mod
    Sx=(Sx*pow(10,(r+1)*len(str(C)),mod))%mod
    C-=(r+1)*B
    now+=r+1
print(ans)

Fixed submission:
L,A,B,M=map(int,input().split())
C=(L-1)*B+A
mod=M
X,s=0,A
now=A
data=[0]*19
ruiseki=[0]*19
Ami=(A-1)//B
Cmi=C//B
for i in range(19):
    now=10**i-1
    if now<A:
        ruiseki[i]=0
    elif now>=C:
        ruiseki[i]=L
    else:
        ruiseki[i]=(now-A)//B+1
def mul33(A,B):
    global mod
    res=[[0]*3 for i in range(3)]
    for i in range(3):
        for j in range(3):
            res[i][j]=sum([A[i][k]*B[k][j]%mod for k in range(3)])
    return res
def ruijou(vec,Cd):
    rui=dict()
    if Cd==0:
        return [[1,0,0],[0,1,0],[0,0,1]]
    now=vec
    ans=[[1,0,0],[0,1,0],[0,0,1]]
    Cds=bin(Cd)[2:][::-1]
    for i in range(len(Cds)):
        if Cds[i]=="1":
            ans=mul33(ans,now)
        now=mul33(now,now)
    return ans
def mul(X,s,Cd,d):
    global mod
    global B
    vec=[[pow(10,d,mod),0,0],[1,1,0],[0,B,1]]
    vec=ruijou(vec,Cd)
    Xc=X
    sc=s
    X=(Xc*vec[0][0]+sc*vec[1][0]+vec[2][0])%mod
    s=(Xc*vec[0][1]+sc*vec[1][1]+vec[2][1])%mod
    return X,s
for d in range(1,19):
    Cd=ruiseki[d]-ruiseki[d-1]
    X,s=mul(X,s,Cd,d)
print(X)

Buggy python submission (verdict: Runtime Error):
L,A,B,M=map(int,input().split())
mod=M
C=A+B*(L-1)
ans=0
def S(x,l,r,mod):
    if l==r:
        return pow(x,l,mod)
    rev=pow(x-1,mod-2,mod)
    return (pow(x,r+1,mod)-pow(x,l,mod))*rev%mod
def SS(x,l,r,mod):
    if l==r:
        return l*pow(x,l,mod)%mod
    rev=pow(x-1,mod-2,mod)
    return rev*(r*pow(x,r+1,mod)-l*pow(x,l,mod)-S(x,l+1,r,mod))%mod
now=0
Sx=1
times=len(str(C))
for dL in range(times,0,-1):
    if len(str(C))==1:
        r=C//B
    else:
        r=(C%pow(10,len(str(C))-1))//B
    if r==0:
        ans=(ans+C)%mod
    else:
        if now+r>=L:
            r=L-now-1
        x=pow(10,len(str(C)),mod)
        y=Sx*(C*(S(x,1,r,mod)+1)-B*SS(x,1,r,mod))%mod
        ans=(ans+y)%mod
    Sx=Sx*pow(10,(r+1)*len(str(C)),mod)%mod
    C-=(r+1)*B
    now+=r+1
print(ans)

Fixed submission:
L,A,B,M=map(int,input().split())
C=(L-1)*B+A
mod=M
X,s=0,A
now=A
data=[0]*19
ruiseki=[0]*19
Ami=(A-1)//B
Cmi=C//B
for i in range(19):
    now=10**i-1
    if now<A:
        ruiseki[i]=0
    elif now>=C:
        ruiseki[i]=L
    else:
        ruiseki[i]=(now-A)//B+1
def mul33(A,B):
    global mod
    res=[[0]*3 for i in range(3)]
    for i in range(3):
        for j in range(3):
            res[i][j]=sum([A[i][k]*B[k][j]%mod for k in range(3)])
    return res
def ruijou(vec,Cd):
    rui=dict()
    if Cd==0:
        return [[1,0,0],[0,1,0],[0,0,1]]
    now=vec
    ans=[[1,0,0],[0,1,0],[0,0,1]]
    Cds=bin(Cd)[2:][::-1]
    for i in range(len(Cds)):
        if Cds[i]=="1":
            ans=mul33(ans,now)
        now=mul33(now,now)
    return ans
def mul(X,s,Cd,d):
    global mod
    global B
    vec=[[pow(10,d,mod),0,0],[1,1,0],[0,B,1]]
    vec=ruijou(vec,Cd)
    Xc=X
    sc=s
    X=(Xc*vec[0][0]+sc*vec[1][0]+vec[2][0])%mod
    s=(Xc*vec[0][1]+sc*vec[1][1]+vec[2][1])%mod
    return X,s
for d in range(1,19):
    Cd=ruiseki[d]-ruiseki[d-1]
    X,s=mul(X,s,Cd,d)
print(X)