Buggy python submission (verdict: Runtime Error):
def cmb(n, r, p):
    if (r < 0) or (n < r):
        return 0
    r = min(r, n - r)
    return fact[n] * factinv[r] * factinv[n-r] % p

p = 10 ** 9 + 7
N = 10 ** 6 + 10 # N は必要分だけ用意する
fact = [1, 1]  # fact[n] = (n! mod p)
factinv = [1, 1]  # factinv[n] = ((n!)^(-1) mod p)
inv = [0, 1]  # factinv 計算用
 
for i in range(2, N + 1):
    fact.append((fact[-1] * i) % p)
    inv.append((-inv[p % i] * (p // i)) % p)
    factinv.append((factinv[-1] * inv[-1]) % p)

k=int(input())
s=input()
lens=len(s)
mod=10**9+7
ans=0

now=1

for i in range(k+1):
    ans+=pow(25,i,mod)*pow(26,k-i,mod)*cmb(lens+i-1,lens-1,mod)
    ans=ans%mod

print(ans)

Fixed submission:
def cmb(n, r, p):
    if (r < 0) or (n < r):
        return 0
    r = min(r, n - r)
    return fact[n] * factinv[r] * factinv[n-r] % p

p = 10 ** 9 + 7
N = 2 * 10 ** 6 + 10 # N は必要分だけ用意する
fact = [1, 1]  # fact[n] = (n! mod p)
factinv = [1, 1]  # factinv[n] = ((n!)^(-1) mod p)
inv = [0, 1]  # factinv 計算用
 
for i in range(2, N + 1):
    fact.append((fact[-1] * i) % p)
    inv.append((-inv[p % i] * (p // i)) % p)
    factinv.append((factinv[-1] * inv[-1]) % p)

k=int(input())
s=input()
lens=len(s)
mod=10**9+7
ans=0

now=1

for i in range(k+1):
    ans+=pow(25,i,mod)*pow(26,k-i,mod)*cmb(lens+i-1,lens-1,mod)
    ans=ans%mod

print(ans)

Buggy python submission (verdict: Runtime Error):
def cmb(n, r, p):
    if (r < 0) or (n < r):
        return 0
    r = min(r, n - r)
    return fact[n] * factinv[r] * factinv[n-r] % p

p = 10 ** 9 + 7
N = 10 ** 6  # N は必要分だけ用意する
fact = [1, 1]  # fact[n] = (n! mod p)
factinv = [1, 1]  # factinv[n] = ((n!)^(-1) mod p)
inv = [0, 1]  # factinv 計算用
 
for i in range(2, N + 1):
    fact.append((fact[-1] * i) % p)
    inv.append((-inv[p % i] * (p // i)) % p)
    factinv.append((factinv[-1] * inv[-1]) % p)

k=int(input())
s=input()
lens=len(s)
mod=10**9+7
ans=0


now=1

for i in range(k+1):
    ans+=pow(25,i,mod)*pow(26,k-i,mod)*cmb(lens+i-1,lens-1,mod)
    ans=ans%mod

print(ans)

Fixed submission:
def cmb(n, r, p):
    if (r < 0) or (n < r):
        return 0
    r = min(r, n - r)
    return fact[n] * factinv[r] * factinv[n-r] % p

p = 10 ** 9 + 7
N = 2 * 10 ** 6 + 10 # N は必要分だけ用意する
fact = [1, 1]  # fact[n] = (n! mod p)
factinv = [1, 1]  # factinv[n] = ((n!)^(-1) mod p)
inv = [0, 1]  # factinv 計算用
 
for i in range(2, N + 1):
    fact.append((fact[-1] * i) % p)
    inv.append((-inv[p % i] * (p // i)) % p)
    factinv.append((factinv[-1] * inv[-1]) % p)

k=int(input())
s=input()
lens=len(s)
mod=10**9+7
ans=0

now=1

for i in range(k+1):
    ans+=pow(25,i,mod)*pow(26,k-i,mod)*cmb(lens+i-1,lens-1,mod)
    ans=ans%mod

print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
def cmb(n, r, p):
    if (r < 0) or (n < r):
        return 0
    r = min(r, n - r)
    return fact[n] * factinv[r] * factinv[n-r] % p

p = 10 ** 9 + 7
N = 10 ** 6  # N は必要分だけ用意する
fact = [1, 1]  # fact[n] = (n! mod p)
factinv = [1, 1]  # factinv[n] = ((n!)^(-1) mod p)
inv = [0, 1]  # factinv 計算用
 
for i in range(2, N + 1):
    fact.append((fact[-1] * i) % p)
    inv.append((-inv[p % i] * (p // i)) % p)
    factinv.append((factinv[-1] * inv[-1]) % p)

k=int(input())
s=input()
lens=len(s)
mod=10**9+7
ans=0

dp=[0 for i in range(1+len(s)+k)]
dp[0]=1




l={i:1 for i in range(lens+10)}
for i in range(lens+1,lens+k+2):
    l[i]=l[i-1]*i//(i-lens)

now=1

for i in range(k+1):
    ans+=pow(25,i,mod)*pow(26,k-i,mod)*cmb(lens+i-1,lens-1,mod)
    ans=ans%mod

print(ans)

Fixed submission:
def cmb(n, r, p):
    if (r < 0) or (n < r):
        return 0
    r = min(r, n - r)
    return fact[n] * factinv[r] * factinv[n-r] % p

p = 10 ** 9 + 7
N = 2 * 10 ** 6 + 10 # N は必要分だけ用意する
fact = [1, 1]  # fact[n] = (n! mod p)
factinv = [1, 1]  # factinv[n] = ((n!)^(-1) mod p)
inv = [0, 1]  # factinv 計算用
 
for i in range(2, N + 1):
    fact.append((fact[-1] * i) % p)
    inv.append((-inv[p % i] * (p // i)) % p)
    factinv.append((factinv[-1] * inv[-1]) % p)

k=int(input())
s=input()
lens=len(s)
mod=10**9+7
ans=0

now=1

for i in range(k+1):
    ans+=pow(25,i,mod)*pow(26,k-i,mod)*cmb(lens+i-1,lens-1,mod)
    ans=ans%mod

print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
def cmb(n, r, p):
    if (r < 0) or (n < r):
        return 0
    r = min(r, n - r)
    return fact[n] * factinv[r] * factinv[n-r] % p

p = 10 ** 9 + 7
N = 10 ** 6  # N は必要分だけ用意する
fact = [1, 1]  # fact[n] = (n! mod p)
factinv = [1, 1]  # factinv[n] = ((n!)^(-1) mod p)
inv = [0, 1]  # factinv 計算用
 
for i in range(2, N + 1):
    fact.append((fact[-1] * i) % p)
    inv.append((-inv[p % i] * (p // i)) % p)
    factinv.append((factinv[-1] * inv[-1]) % p)

k=int(input())
s=input()
lens=len(s)
mod=10**9+7
ans=0

dp=[0 for i in range(1+len(s)+k)]
dp[0]=1

import math
def  mcal(n,r):
    return math.factorial(n)//math.factorial(n-r)//math.factorial(r)


l={i:1 for i in range(lens+10)}
for i in range(lens+1,lens+k+2):
    l[i]=l[i-1]*i//(i-lens)

now=1

for i in range(k+1):
    ans+=pow(25,i,mod)*pow(26,k-i,mod)*cmb(lens+i-1,lens-1,mod)
    ans=ans%mod

print(ans)

Fixed submission:
def cmb(n, r, p):
    if (r < 0) or (n < r):
        return 0
    r = min(r, n - r)
    return fact[n] * factinv[r] * factinv[n-r] % p

p = 10 ** 9 + 7
N = 2 * 10 ** 6 + 10 # N は必要分だけ用意する
fact = [1, 1]  # fact[n] = (n! mod p)
factinv = [1, 1]  # factinv[n] = ((n!)^(-1) mod p)
inv = [0, 1]  # factinv 計算用
 
for i in range(2, N + 1):
    fact.append((fact[-1] * i) % p)
    inv.append((-inv[p % i] * (p // i)) % p)
    factinv.append((factinv[-1] * inv[-1]) % p)

k=int(input())
s=input()
lens=len(s)
mod=10**9+7
ans=0

now=1

for i in range(k+1):
    ans+=pow(25,i,mod)*pow(26,k-i,mod)*cmb(lens+i-1,lens-1,mod)
    ans=ans%mod

print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
k=int(input())
s=input()
lens=len(s)
mod=10**9+7
ans=0

dp=[0 for i in range(1+len(s)+k)]
dp[0]=1

import math
def  mcal(n,r):
    return math.factorial(n)//math.factorial(n-r)//math.factorial(r)

l={i:1 for i in range(lens+10)}
for i in range(lens+1,lens+k+2):
    l[i]=l[i-1]*i//(i-lens)

now=1

for i in range(k+1):
    ans+=pow(25,i,mod)*pow(26,k-i,mod)*mcal(lens+i-1,lens-1)
    ans=ans%mod

print(ans)

Fixed submission:
def cmb(n, r, p):
    if (r < 0) or (n < r):
        return 0
    r = min(r, n - r)
    return fact[n] * factinv[r] * factinv[n-r] % p

p = 10 ** 9 + 7
N = 2 * 10 ** 6 + 10 # N は必要分だけ用意する
fact = [1, 1]  # fact[n] = (n! mod p)
factinv = [1, 1]  # factinv[n] = ((n!)^(-1) mod p)
inv = [0, 1]  # factinv 計算用
 
for i in range(2, N + 1):
    fact.append((fact[-1] * i) % p)
    inv.append((-inv[p % i] * (p // i)) % p)
    factinv.append((factinv[-1] * inv[-1]) % p)

k=int(input())
s=input()
lens=len(s)
mod=10**9+7
ans=0

now=1

for i in range(k+1):
    ans+=pow(25,i,mod)*pow(26,k-i,mod)*cmb(lens+i-1,lens-1,mod)
    ans=ans%mod

print(ans)