Problem:
Score : 400 points

Problem Statement

The ABC number of a string T is the number of triples of integers (i, j, k) that satisfy all of the following conditions:

1 ≤ i < j < k ≤ |T| (|T| is the length of T.)

T_i = A (T_i is the i-th character of T from the beginning.)

T_j = B

T_k = C

For example, when T = ABCBC, there are three triples of integers (i, j, k) that satisfy the conditions: (1, 2, 3), (1, 2, 5), (1, 4, 5). Thus, the ABC number of T is 3.

You are given a string S. Each character of S is A, B, C or ?.

Let Q be the number of occurrences of ? in S. We can make 3^Q strings by replacing each occurrence of ? in S with A, B or C. Find the sum of the ABC numbers of all these strings.

This sum can be extremely large, so print the sum modulo 10^9 + 7.

Constraints

3 ≤ |S| ≤ 10^5

Each character of S is A, B, C or ?.

Input

Input is given from Standard Input in the following format:

S

Output

Print the sum of the ABC numbers of all the 3^Q strings, modulo 10^9 + 7.

Sample Input 1

A??C

Sample Output 1

8

In this case, Q = 2, and we can make 3^Q = 9 strings by by replacing each occurrence of ? with A, B or C. The ABC number of each of these strings is as follows:

AAAC: 0

AABC: 2

AACC: 0

ABAC: 1

ABBC: 2

ABCC: 2

ACAC: 0

ACBC: 1

ACCC: 0

The sum of these is 0 + 2 + 0 + 1 + 2 + 2 + 0 + 1 + 0 = 8, so we print 8 modulo 10^9 + 7, that is, 8.

Sample Input 2

ABCBC

Sample Output 2

3

When Q = 0, we print the ABC number of S itself, modulo 10^9 + 7. This string is the same as the one given as an example in the problem statement, and its ABC number is 3.

Sample Input 3

????C?????B??????A???????

Sample Output 3

979596887

In this case, the sum of the ABC numbers of all the 3^Q strings is 2291979612924, and we should print this number modulo 10^9 + 7, that is, 979596887.

Solution in C (GCC 5.4.1) (judge verdict: Wrong Answer)

#include<stdio.h>
#include<stdlib.h>
#include <string.h>

long power(long m, long n);
long

int main(void)
{
    char s[100001],abc[3]={'A','B','C'};
    long i,j,k,sum=0,length,q=0,dp[100000][4],m,m1,m2;
    
    scanf("%s",s);

    length=strlen(s);

    dp[length][3]=1;
    for ( j = 0; j < 3; j++)
    {
        dp[length][j]=0;
    }
    for ( i = length-1; i >=0 ; i--)
    {
        if(s[i]=='?') m=3;
        else m=1;
        dp[i][3]=m*dp[i+1][3];
    }

    for ( i = length-1; i >=0; i--)
    {
        for(j=2;j>=0;j--)
        {
            if(s[i]=='?') m1=3;
            else m1=1;
            if(s[i]=='?'||s[i]==abc[j]) m2=1;
            else m2=0;
            dp[i][j]=m1*dp[i+1][j]+m2*dp[i+1][j+1];
        }
    }

    printf("%ld",dp[0][0]%(1000000000+7));

    return 0;
}