#include <stdio.h>
#include<malloc.h>
int main() {
int times ;
scanf("%d",×);
int queue[100000];
int head =0;
int tail = 0;
for(int i=0;i<times;i++){
char* op = (char*)malloc(sizeof(char)*6);
scanf("%s",op);
if(!strcmp(op,"push")){
int tmp;
scanf("%d",&tmp);
queue[tail++] = tmp;
}
if(!strcmp(op,"pop")){
if(tail<=head){
printf("error\n");
}else{
printf("%d\n",queue[head++]);
}
}
if(!strcmp(op, "front")){
if(tail<=head){
printf("error\n");
}
else{
printf("%d\n",queue[head]);
}
}
}
return 0;
}

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