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: Runtime Error)

#include<stdio.h>
#include<math.h>

int main(){
	char s[10001];	int q=0;
	scanf("%s",s);
	int i;
	for(i=0;s[i]!='\0';i++) {
		if(s[i]=='?') q++;
	}
	
	int j,k,ac,bc,cc;
	long sum=0;
	for(i=0;s[i]!='\0';i++) {
		if(s[i]=='?') ac=1;
		if(s[i]=='A'||s[i]=='?') {
			for(j=i+1;s[j]!='\0';j++) {
				bc=ac;
				if(s[j]=='?') bc++;
				if(s[j]=='B'||s[j]=='?') {
					for(k=j+1;s[k]!='\0';k++) {
						cc=bc;
						if(s[k]=='?') cc++;
						if(s[k]=='C'||s[k]=='?') {
							sum+=pow(3,q-cc);
						}
					}
				}
			}
		}
		ac=0;
	}
	
	long ans;
	
	ans = sum%1000000007;
	
	printf("%ld",ans);
	
	return 0;
}