#include <bits/stdc++.h>
using namespace std;
char charOfStep[1000005];
int depth[1000005];
int kthAncestor[1000005][21];
int curStep = 0;
void Init() {}
void TypeLetter(char L) {
curStep++;
charOfStep[curStep] = L;
depth[curStep] = depth[curStep-1]+1;
kthAncestor[curStep][0] = curStep-1;
for(int i = 1; 1<<i <= depth[curStep]; i++)
kthAncestor[curStep][i] = kthAncestor[kthAncestor[curStep][i-1]][i-1];
}
void UndoCommands(int U) {
curStep++;
charOfStep[curStep] = charOfStep[curStep-1-U];
depth[curStep] = depth[curStep-1-U];
copy(kthAncestor[curStep], kthAncestor[curStep]+21, kthAncestor[curStep-1-U]);
}
char GetLetter(int P) {
int node = curStep;
for(int i = 21; i >= 0; i--)
if(depth[node] - (1<<i) >= P+1)
node = kthAncestor[node][i];
return charOfStep[node];
}
