#include<stdio.h>
#include<string.h>
int arr[100000];
int main()
{
    int n,num,count=0;
    char temp[100];
    scanf("%d",&n);
    for(int index=0;index<n;index++)
    {
        scanf("%s",temp);
        if(strcmp(temp,"push")==0) scanf("%d",&arr[count++]);
        else if(strcmp(temp,"pop")==0&&count-1>=0) 
        printf("%d\n",arr[--count]);
        else if(strcmp(temp,"top")==0&&count-1>=0) 
        printf("%d\n",arr[count-1]);
        else printf("error\n");
    }
    puts("\n");
    return 0;
}