//Zory-2020
#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
// typedef __int128 ll;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
#define FR first
#define SE second
#define MP make_pair
#define PB push_back
#define vc vector
#define all(x) (x).begin(),(x).end()
#define sz(x) ((int)(x).size())
#define bin(x) (1ll<<(x))
#define fo(i,l,r) for(int i=(l),I=(r);i<=I;i++)
#define fd(i,r,l) for(int i=(r),I=(l);i>=I;i--)
#define mem(x,val) memset(x,val,sizeof x)
bool DD=0;
#define Debug if(DD) printf("line %d\n",__LINE__)
#define deb(x) if(DD) cerr<<#x<<'='<<x<<endl
#define debug if(DD) printf
namespace mine
{
    ll qread()
    {
        ll ans=0,f=1;char c=getchar();
        while(c<'0' or c>'9') {if(c=='-')f=-1;c=getchar();}
        while('0'<=c and c<='9') ans=ans*10+c-'0',c=getchar();
        return ans*f;
    }
    void write(ll num){if(num<0) putchar('-'),num=-num;if(num>=10) write(num/10);putchar('0'+num%10);}
    void write1(ll num){write(num);putchar(' ');}
    void write2(ll num){write(num);putchar('\n');}
    template<typename T>inline bool chmax(T&a,const T&b){return a<b?a=b,1:0;}
    template<typename T>inline bool chmin(T&a,const T&b){return a>b?a=b,1:0;}
    ll gcd(ll x,ll y){return y?gcd(y,x%y):x;}
    bool IN(ll x,ll l,ll r){return l<=x and x<=r;}

    const int INF=0x3f3f3f3f;
    const int MOD=1e9+9;
    int mm(const int x){return x>=MOD?x-MOD:x;}
    template<typename T> void add(T &x,const int &y){x=(x+y>=MOD?x+y-MOD:x+y);}
    ll qpower(ll x,ll e,int mod=MOD){ll ans=1;while(e){if(e&1)ans=ans*x%mod;x=x*x%mod;e>>=1;}return ans;}
    ll invm(ll x){return qpower(x,MOD-2);}
    const int N=1e6+10;

	map<string,int> A;
	int ask(string str){
		if(A.count(str)) return A[str];
		cout<<str<<endl;fflush(stdout);
		int ret=qread();if(!ret) exit(0);
		return A[str]=ret;
	}
    void main()
    {
		string now="";fo(i,1,300) now=now+"a";int aa=300-ask(now);
		now="";fo(i,1,300) now=now+"b";int bb=300-ask(now),n=aa+bb;
		if(bb==0){ now="";fo(i,1,n) now=now+"a";ask(now); }//debug
		now="";
		int pos=0;//pos和pos+1之间
		fd(left,bb,1)
		{
			string hh=now+"b";fo(i,pos+1,aa) hh+="a";
			if(ask(hh)==n-sz(hh)) now+="b"; else left++,pos++,now+="a";
		}
    }
};//(ans+MOD)%MOD
signed main()
{
    //freopen("a.in","r",stdin);
    //freopen("z.txt","r",stdin);
    srand(time(0));
    mine::main();
}