inputs: Solve in Python:
There is a game that involves three variables, denoted A, B, and C.
As the game progresses, there will be N events where you are asked to make a choice.
Each of these choices is represented by a string s_i. If s_i is AB, you must add 1 to A or B then subtract 1 from the other; if s_i is AC, you must add 1 to A or C then subtract 1 from the other; if s_i is BC, you must add 1 to B or C then subtract 1 from the other.
After each choice, none of A, B, and C should be negative.
Determine whether it is possible to make N choices under this condition. If it is possible, also give one such way to make the choices.

-----Constraints-----
 - 1 \leq N \leq 10^5
 - 0 \leq A,B,C \leq 10^9
 - N, A, B, C are integers.
 - s_i is AB, AC, or BC.

-----Input-----
Input is given from Standard Input in the following format:
N A B C
s_1
s_2
:
s_N

-----Output-----
If it is possible to make N choices under the condition, print Yes; otherwise, print No.
Also, in the former case, show one such way to make the choices in the subsequent N lines. The (i+1)-th line should contain the name of the variable (A, B, or C) to which you add 1 in the i-th choice.

-----Sample Input-----
2 1 3 0
AB
AC

-----Sample Output-----
Yes
A
C

You can successfully make two choices, as follows:
 - In the first choice, add 1 to A and subtract 1 from B. A becomes 2, and B becomes 2.
 - In the second choice, add 1 to C and subtract 1 from A. C becomes 1, and A becomes 1.
targets: N, A, B, C = map(int, input().split())
S = [input() for _ in range(N)]
ans = []
for i, s in enumerate(S):
    if s == "AB":
        if A == 0:
            A += 1
            B -= 1
            ans.append("A")
        elif B == 0:
            A -= 1
            B += 1
            ans.append("B")
        else:
            if i + 1 == N or S[i + 1] == "AB":
                A += 1
                B -= 1
                ans.append("A")
            else:
                if S[i + 1] == "BC":
                    A -= 1
                    B += 1
                    ans.append("B")
                else:
                    A += 1
                    B -= 1
                    ans.append("A")

        if A < 0 or B < 0:
            print("No")
            return
    elif s == "BC":
        if B == 0:
            B += 1
            C -= 1
            ans.append("B")
        elif C == 0:
            B -= 1
            C += 1
            ans.append("C")
        else:
            if i + 1 == N or S[i + 1] == "BC":
                B += 1
                C -= 1
                ans.append("B")
            else:
                if S[i + 1] == "AB":
                    B += 1
                    C -= 1
                    ans.append("B")
                else:
                    B -= 1
                    C += 1
                    ans.append("C")

        if B < 0 or C < 0:
            print("No")
            return
    else:
        if C == 0:
            C += 1
            A -= 1
            ans.append("C")
        elif A == 0:
            C -= 1
            A += 1
            ans.append("A")
        else:
            if i + 1 == N or S[i + 1] == "AC":
                A += 1
                C -= 1
                ans.append("A")
            else:
                if S[i + 1] == "AB":
                    A += 1
                    C -= 1
                    ans.append("A")
                else:
                    A -= 1
                    C += 1
                    ans.append("C")

        if A < 0 or C < 0:
           ...