输入月份序号输出该月英文名，输入0程序结束，我写的这个输入负数就有乱码什么原因？

Question

#include<stdio.h>main(){ char a[15][20]={"January","February","March","April","May","June","July","August","September","October","November","December"}; int x; while(x!=0) { scanf("%d",&x); if(x<0||x>12) printf("error\n"); printf("%s\n",a[x-1]); } }