c语言编程练习题：7-46 爬动的蠕虫

#include <stdio.h>

int main(){

   int N,U,D;

   int len=0;

   int direction=1;

   int count=0;

   if (scanf("%d",&N)!=EOF && scanf("%d",&U)!=EOF && scanf("%d",&D)!=EOF){

       while (len<N){

           if (direction==1){len = len+direction*U;}

           if (direction==-1){len = len+direction*D;}

           direction = direction*-1;

           count++;

           if (len>=N){break;}

       }

       printf("%d",count);

   }else{

       printf("something wrong when input N,U,D");

   }

   return 0;

}