#include<stdio.h>
#include<stdlib.h>
int main()
{
  char
 
 num[51]={'\0'};
  int i=0,length=0;
  double result=0,t=0;
  scanf("%s",num);
  while(num[i]!='\0')
  {
    if(num[i]=='2')
    {
      t++;
    }
    i++;
  }
  if(num[0]=='-')
  {
    length=i-1;
    if(num[length]=='2'||num[length]=='4'||num[length]=='6'||num[length]=='8'||num[length]=='0')
    {
      result=t/length*1
 
.5*2*100;
    }
    else result=t/length*1.5*100;
  }
  else 
  {
    length=i;
    if(num[length-1]=='2'||num[length-1]=='4'||num[length-1]=='6'||num[length-1]=='8'||num[length-1]=='0')
    {
      result=t/length*2*100;
    }
    else result=t/length*100;
  }
  printf("%.2lf%%",result);

}