哪位大佬帮我看看？只有80分。

#include <bits/stdc++.h>
using namespace std;
int main(){
	int t;
	int n;
	string s,s2;
	cin>>t;
	for(int i=1;i<=t;i++){
		cin>>n;
		int sum=0;
		cin>>s;
		s2=s;
		bool l=0;
		for(int j=0;j<n;j++){
			if(s[j]!='A'||s[j]!='T'||s[j]!='C'||s[j]!='G'){
				//
			}else{
				l=1;
				break;
			}
		}
		reverse(s.begin(),s.end());
		for(int j=0;j<n;j++){
			if(s[j]=='A'&&s2[j]=='T'){
				sum=sum+j+1;
			}else if(s[j]=='T'&&s2[j]=='A'){
				sum=sum+j+1;
			}else if(s[j]=='C'&&s2[j]=='G'){
				sum=sum+j+1;
			}else if(s[j]=='G'&&s2[j]=='C'){
				sum=sum+j+1;
			}
		}
		if(l==1)sum=0;
		cout<<sum<<endl;
	}
    return 0;
}