#include <stdio.h>
int main(void){
	char S[10];
	char ans[10] = "yukicoder"; 
	
	scanf("%s",S);
	
	for(int i = 0; i < 9; i++){
		if(S[i] != ans[i]){
			printf("%c\n",ans[i]);
			return 0;
		}
	}
	printf("error\n");
	return 0;
}