#include<bits/stdc++.h>
using namespace std;
inline long long read(){
long long num=0;int z=1;char c=getchar();
if(c=='-') z=-1;
while((c<'0'||c>'9')&&c!='-') c=getchar();
if(c=='-') z=-1,c=getchar();
while(c>='0'&&c<='9') num=(num<<1)+(num<<3)+(c^48),c=getchar();
return z*num;
}
char s[106];
int main(){
priority_queue<int>a;
int n;
n=read();
int l;
for(int i=1;i<=n;i++)
{
scanf("%s",s+1);
if(s[1]=='A'){
l=read();
a.push(-l);
}
else{
if(a.empty())
{
printf("ERROR
");
}
else{
printf("%d
",-a.top());
a.pop();
}
}
}
return 0;
}