#include<iostream>
#include<cstring>
using namespace std;
int m,t,n;
int neicun[101],biaohao;
string a;
bool pd;
int main(){
	cin>>t>>m;
	while(t--){
		cin>>a;
		if(a!="defragment") cin>>n;
		if(a=="alloc"){
			bool pdalloc=0;
			for(int i=1;i<=m-n+1;i++){
				pd=0;
				for(int j=0;j<n;j++)
					if(neicun[i+j]!=0){
						pd=1;
						break;
					}
				if(pd==0){
					biaohao++;
					for(int j=0;j<n;j++) neicun[i+j]=biaohao;
					pdalloc=1;
					break;
				}
			}
			if(pdalloc==1) cout<<biaohao<<endl;
			else cout<<"NULL"<<endl;
		}
		else if(a=="erase"){
			bool pderase=0;
			if(n==0){
				cout<<"ILLEGAL_ERASE_ARGUMENT"<<endl;	
				continue;
			}
			for(int i=1;i<=m;i++) if(neicun[i]==n) neicun[i]=0,pderase=1;
			if(pderase==0) cout<<"ILLEGAL_ERASE_ARGUMENT"<<endl;
		}	
		else{
			int kong=1;
			for(int i=1;i<=m;i++)
				if(neicun[i]!=0){
					while(neicun[kong]!=0) kong++;
					if(kong<=i) neicun[kong]=neicun[i],neicun[i]=0;
				}
		}
	}
	return 0;
}