Buggy python submission (verdict: Time Limit Exceeded):
#!/usr/bin/env python3
import sys, math, fractions, itertools

def solve(N: int, A: int, x: "List[int]"):
    X = max(x)
    dp = [[[0 for _ in range(max(N*X+1, N*A+1))] for _ in range(N+1) ] for _ in range(N+1)]
    dp[0][0][0] = 1
    for n in range(N+1):
        for m in range(N+1):
            for k in range(N*X+1):
                if n >= 1 and k < x[n-1]:
                    dp[n][m][k] = dp[n-1][m][k]
                elif n >= 1 and m >= 1 and k >= x[n-1]:
                    dp[n][m][k] = dp[n-1][m][k] + dp[n-1][m-1][k-x[n-1]]
    s = 0
    for i in range(1, N+1):
        s += dp[N][i][i*A]
    print(s)
    return


# Generated by 1.1.4 https://github.com/kyuridenamida/atcoder-tools  (tips: You use the default template now. You can remove this line by using your custom template)
def main():
    def iterate_tokens():
        for line in sys.stdin:
            for word in line.split():
                yield word
    tokens = iterate_tokens()
    N = int(next(tokens))  # type: int
    A = int(next(tokens))  # type: int
    x = [ int(next(tokens)) for _ in range(N) ]  # type: "List[int]"
    solve(N, A, x)

if __name__ == '__main__':
    main()


Fixed submission:
#!/usr/bin/env python3
import sys, math, fractions, itertools

def solve(N: int, A: int, x: "List[int]"):
    X = max(x)
    dp = [[[0 for _ in range(max(N*X+1, N*A+1))] for _ in range(N+1) ] for _ in range(N+1)]
    dp[0][0][0] = 1
    for n in range(N+1):
        for m in range(N+1):
            for k in range(N*X+1):
                if n >= 1 and k < x[n-1]:
                    dp[n][m][k] = dp[n-1][m][k]
                elif n >= 1 and m >= 1 and k >= x[n-1]:
                    dp[n][m][k] = dp[n-1][m][k] + dp[n-1][m-1][k-x[n-1]]
    s = 0
    for i in range(1, N+1):
        s += dp[N][i][i*A]
    print(s)
    return


# Generated by 1.1.4 https://github.com/kyuridenamida/atcoder-tools  (tips: You use the default template now. You can remove this line by using your custom template)
def main():
    def iterate_tokens():
        for line in sys.stdin:
            for word in line.split():
                yield word
    tokens = iterate_tokens()
    N = int(next(tokens))  # type: int
    A = int(next(tokens))  # type: int
    x = [ int(next(tokens)) for _ in range(N) ]  # type: "List[int]"
    solve(N, A, x)

if __name__ == '__main__':
    main()

Buggy python submission (verdict: Runtime Error):
#!/usr/bin/env python3
import sys, math, fractions, itertools

def solve(N: int, A: int, x: "List[int]"):
    X = max(x)
    dp = [[[0 for _ in range(N*X+1)] for _ in range(N+1) ] for _ in range(N+1)]
    dp[0][0][0] = 1
    for n in range(N+1):
        for m in range(N+1):
            for k in range(N*X+1):
                if n >= 1 and k < x[n-1]:
                    dp[n][m][k] = dp[n-1][m][k]
                elif n >= 1 and m >= 1 and k >= x[n-1]:
                    dp[n][m][k] = dp[n-1][m][k] + dp[n-1][m-1][k-x[n-1]]
    s = 0
    for i in range(1, N+1):
        s += dp[N][i][i*A]
    print(s)
    return


# Generated by 1.1.4 https://github.com/kyuridenamida/atcoder-tools  (tips: You use the default template now. You can remove this line by using your custom template)
def main():
    def iterate_tokens():
        for line in sys.stdin:
            for word in line.split():
                yield word
    tokens = iterate_tokens()
    N = int(next(tokens))  # type: int
    A = int(next(tokens))  # type: int
    x = [ int(next(tokens)) for _ in range(N) ]  # type: "List[int]"
    solve(N, A, x)

if __name__ == '__main__':
    main()


Fixed submission:
#!/usr/bin/env python3
import sys, math, fractions, itertools

def solve(N: int, A: int, x: "List[int]"):
    X = max(x)
    dp = [[[0 for _ in range(max(N*X+1, N*A+1))] for _ in range(N+1) ] for _ in range(N+1)]
    dp[0][0][0] = 1
    for n in range(N+1):
        for m in range(N+1):
            for k in range(N*X+1):
                if n >= 1 and k < x[n-1]:
                    dp[n][m][k] = dp[n-1][m][k]
                elif n >= 1 and m >= 1 and k >= x[n-1]:
                    dp[n][m][k] = dp[n-1][m][k] + dp[n-1][m-1][k-x[n-1]]
    s = 0
    for i in range(1, N+1):
        s += dp[N][i][i*A]
    print(s)
    return


# Generated by 1.1.4 https://github.com/kyuridenamida/atcoder-tools  (tips: You use the default template now. You can remove this line by using your custom template)
def main():
    def iterate_tokens():
        for line in sys.stdin:
            for word in line.split():
                yield word
    tokens = iterate_tokens()
    N = int(next(tokens))  # type: int
    A = int(next(tokens))  # type: int
    x = [ int(next(tokens)) for _ in range(N) ]  # type: "List[int]"
    solve(N, A, x)

if __name__ == '__main__':
    main()