#include<stdio.h> void main() { int w; scanf("%d,&w"); switch(w) { case 0:("it's,sunday\n");break; case 1:("it's,monday\n");break; case 2:("it's,tuesday\n");break; case 3:("it's,wednesday\n");break; case 4:("it's,thuesday\n");break; case 5:("it's,friday\n");break; case 6:("it's,saturday\n");break; default:printf("Invalid data!\n");break; } } 能运行但是一输入数字就停止运行,这是为什么?