#include <bits/stdc++.h>
#define MAX 1000010
#define INF INT_MAX
#define MOD 1000000007
#define mp make_pair
#define mt make_tuple
#define pb push_back
#define ins insert
#define ff first
#define ss second
#define gett(x,m) get<m>(x)
#define all(a) a.begin(),a.end()
#define lb(a,b) lower_bound(all(a),b)
#define ub(a,b) upper_bound(all(a),b)
#define sortv(a) sort(all(a))
#define sorta(a,sz) sort(a,a+sz)
#define inputar(a,b){\
for(int i=0;i<b;i++){\
cin >> a[i];\
}\
}
#define inputvec(a,b){\
for(int i=0;i<b;i++){\
ll num;\
cin >> num;\
a.pb(num);\
}\
}
#define outputar(a,b){\
for(int i=0;i<b;i++){\
cout << a[i] << " ";\
}\
cout << "\n";\
}
#define outputvec(a){\
for(auto x:a){\
cout << x << " ";\
}\
cout << "\n";\
}
#define reset(a,n,v){\
for(int i=0;i<n;i++){\
a[i]=v;\
}\
}
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef tuple<ll,ll,ll> tll;
typedef pair<ll,ll> pll;
typedef pair<int,int> pii;
typedef double db;
typedef long double ldb;
inline void USACO(string filename){
freopen((filename+".in").c_str(),"r",stdin);
freopen((filename+".out").c_str(),"w",stdout);
}
int cnt=1;
int lastU=0;
int a[MAX],b[MAX],e[MAX];
vector<vector<int>> c;
vector<int> d;
vector<char> d1;
void Init() {
c.resize(21,vector<int>(MAX,INF));
d.pb(0);
d1.pb('0');
}
void TypeLetter(char L) {
d1.pb(L);
a[cnt]=a[cnt-1]+1;
cnt++;
}
void UndoCommands(int U) {
d1.pb('0');
auto it=lb(d,max(cnt-U,1));
--it;
c[0][cnt]=*it;
int h=*it;
for(int i=1;i<=20;i++){
if(h!=INF){
h=c[i-1][h];
}
c[i][cnt]=h;
}
a[cnt]=a[cnt-1];
b[cnt]=a[max(cnt-U-1,0)]-a[*it]+b[*it];
e[cnt]=U;
lastU=cnt;
d.pb(cnt);
cnt++;
}
char GetLetter(int P) {
a[cnt]=a[cnt-1];
b[cnt]=a[cnt]-a[lastU]+b[lastU];
e[cnt]=0;
P+=1;
int h=lastU;
for(int i=20;i>=0;i--){
if(c[i][h]!=INF && b[c[i][h]]>=P){
h=c[i][h];
}
}
if(b[h]<P){
h=cnt;
}
return d1[h-e[h]-1-(b[h]-P)];
}
