TOPCODER SRM 648 -AB

#include<stdio.h>
#include<iostream>
#include<cstring>
#include<string>
#include<cstdlib>
#include<algorithm>
#include<queue>
#include<vector>
#include<set>
#include<map>
using namespace std;
typedef long long ll;
typedef long double ld;
#define len(a) (int)strlen(a)
#define slen(s) (int)s.length()
#define pb(a) push_back(a)
#define clr(a) memset(a,0,sizeof(a))
#define rep(i, a, b) for (int i = a; i < b; i++)
#define dep(i, a, b) for (int i = a; i > b; i--)
#define repin(i, a, b) for (int i = a; i <= b; i++)
int num[1000];
int main()
{
int n,k;
while(~scanf("%d %d",&n,&k))
{
int n1=(n>>1);
int nt=n1*(n-n1);
if(k>nt) return 0;
clr(num);
while(k)
{
int k1=min(n1,k);
num[k1]+=1;
k-=k1;
}
string res;
repin(i,1,n1)
{
res+="A";
rep(j,0,num[i])
{
res+="B";
}
}
while(slen(res)<n){
res.insert(0,"B");
}
cout<<res<<endl;
}
return 0;
}