L1017到底有多二

#include<stdio.h>#include<string.h>int main(){char a[50];int i,n=0;//2's number//float len,x;    gets(a);len=(float)strlen(a);if(a[0]=='-'){len--;}//len代表其位数//   for(i=0;i<len;i++)if((a[i]-'0')==2){n++;}   x=n/len;   if(a[0]=='-'){          x=x*1.5; }  if((a[(int)len]-'0')%2==0)        {x=x*2;}    printf("%.2f%%",(float)x*100);    return 0;}