40分求助

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <math.h> 
#include <string.h>
using namespace std;
const int N=5;
char a[N];
int main()
{
	cin>>a;
	int len=strlen(a);
	for(int i=1;i<=len;i++){
		if(a[i]!='D'){
			cout<<"This is ok.";
			break;
		}
		else if(a[i]=='A' or a[i]=='B'){
			cout<<"I'm so happy.";
			break;
		}
		else{
			cout<<"Never give up.";
			break;
		}
	}
	return 0;
}