Buggy python submission (verdict: Runtime Error):
def dfs(p,s,c,cmin,cmax):
    if len(p) == 0:
        return solve(s,c,cmin,cmax)
    lower, u = p[0]
    c += lower
    if u <= 9:
        cmin[lower] = 0
        cmax[lower] = u
        return dfs(p[1:],s,c,cmin,cmax)
    
    cmin[lower] = 0
    cmax[lower] = 9
    ret = dfs(p[1:],s,c,cmin,cmax)

    upper = lower.upper()
    s = s.translate(str.maketrans({lower:upper + lower}))

    c += upper
    if u % 10 == 9:
        cmin[upper] = 1
        cmax[upper] = u // 10
        return ret + dfs(p[1:],s,c,cmin,cmax)
    if 20 <= u:
        cmin[upper] = 1
        cmax[upper] = u // 10 - 1
        ret += dfs(p[1:],s,c,cmin,cmax)
    cmin[lower] = 0
    cmax[lower] = u % 10
    cmin[upper] = u // 10
    cmax[upper] = u // 10
    return ret + dfs(p[1:],s,c,cmin,cmax)
def solve(s,c,cmin,cmax):
    uf = {ci:-1 for ci in c}
    for i in range(len(s) // 2):
        join(uf,s[i],s[-i-1])
    nmin,nmax = {},{}
    for ci in c:
        p = root(uf,ci)
        try:
            nmax[p] = min(nmax[p],cmax[ci])
            nmin[p] = max(nmin[p],cmin[ci])
        except KeyError:
            nmax[p] = cmax[ci]
            nmin[p] = cmin[ci]
    
    ret = 1
    for p in nmax.keys():
        if nmax[p] < nmin[p]:
            return 0
        ret *= nmax[p] - nmin[p] + 1
    return ret
def join(uf,p,q):
    p = root(uf,p)
    q = root(uf,q)
    if p == q:
        return
    uf[p] += uf[q]
    uf[q] = p
    
def root(uf,p):
    if isinstance(uf[p], int):
        return p
    uf[p] = root(uf,uf[p])
    return uf[p]
import sys
f = sys.stdin

_, _ = map(int, f.readline().split())
s = f.readline().strip()
p = [line.split() for line in f]
for pi in p:
    pi[1] = int(pi[1])
cmin,cmax = {str(i):i for i in range(10)},{str(i):i for i in range(10)}
characters = '0123456789'
print(dfs(p,s,characters,cmin,cmax) % (10 ** 9 + 7))

Fixed submission:
#@profile
def dfs(p,s,c,cmin,cmax):
    if len(p) == 0:
        return solve(s,c,cmin,cmax)
    lower, u = p[0]
    c += lower
    if u <= 9:
        cmin[lower] = 0
        cmax[lower] = u
        return dfs(p[1:],s,c,cmin,cmax)
     
    cmin[lower] = 0
    cmax[lower] = 9
    ret = dfs(p[1:],s,c,cmin,cmax)
 
    upper = lower.upper()
    s = s.translate(str.maketrans({lower:upper + lower}))
 
    c += upper
    if u % 10 == 9:
        cmin[upper] = 1
        cmax[upper] = u // 10
        return ret + dfs(p[1:],s,c,cmin,cmax)
    if 20 <= u:
        cmin[upper] = 1
        cmax[upper] = u // 10 - 1
        ret += dfs(p[1:],s,c,cmin,cmax)
    cmin[lower] = 0
    cmax[lower] = u % 10
    cmin[upper] = u // 10
    cmax[upper] = u // 10
    return ret + dfs(p[1:],s,c,cmin,cmax)
#@profile
def solve(s,c,cmin,cmax):
    uf = [-1] * 128
    s1 = map(ord,s[:len(s)//2])
    s2 = map(ord,s[::-1][:len(s)//2])
    for p,q in zip(s1,s2):
        p = root(uf,p)
        q = root(uf,q)
        if p != q:
            if uf[p] >= uf[q]:
                uf[p] += uf[q]
                uf[q] = p
            else:
                uf[q] += uf[p]
                uf[p] = q

    nmin,nmax = {},{}
    for ci in c:
        p = root(uf,ord(ci))
        p = str(p)
        try:
            nmax[p] = min(nmax[p],cmax[ci])
            nmin[p] = max(nmin[p],cmin[ci])
        except KeyError:
            nmax[p] = cmax[ci]
            nmin[p] = cmin[ci]
     
    ret = 1
    for p in nmax.keys():
        if nmax[p] < nmin[p]:
            return 0
        ret *= nmax[p] - nmin[p] + 1
    return ret
    
#@profile 
def root(uf,p):
    if uf[p] < 0:
        return p
    uf[p] = root(uf,uf[p])
    return uf[p]

import sys
f = sys.stdin
 
_, _ = map(int, f.readline().split())
s = f.readline().strip()
p = [line.split() for line in f]
for pi in p:
    pi[1] = int(pi[1])
cmin,cmax = {str(i):i for i in range(10)},{str(i):i for i in range(10)}
characters = '0123456789'
print(dfs(p,s,characters,cmin,cmax) % (10 ** 9 + 7))