>>180
#include <stdio.h>
#include <string.h>

int main(void)
{
char str[256];
int top;
printf("入力：");
start:
top=0;
fgets(str,256,stdin);
again0:
if(str[top]>=48&&str[top]<=57){
printf("再入力：");
goto start;
}
if(top++<strlen(str))goto again0;
top=0;
again1:
if(str[top]=='a'){
top++;
goto again1;
}
printf("出力：");
again2:
printf("%c",str[top++]);
if(str[top]!=NULL)goto again2;
return 0;
}