PAT1093解題報告

#include <iostream>
#include <string>
using namespace std;

long long P = 0, PA = 0, PAT = 0;
int main(){
	string A;
	cin>>A;
	for(int i = 0; i < A.length(); ++i){
		if(A[i] == 'P'){
			P++;
		}else if(A[i] == 'A'){
			PA += P;
		}else if(A[i] == 'T'){
			PAT += PA;
		}
	}
	cout<<PAT % 1000000007<<endl;
	return 0;
}