杭电2131

#include <iostream>
#include <cstdio>
#include <cstring>
using namespace std;
int main()
{
char ch[2];
char s1[210];
int len,i,j,sum;
while(~scanf("%s%s",ch,s1))
{
sum=0;
len=strlen(s1);
if(ch[0]>='A'&&ch[0]<='Z')
{
for(i=0;i<len;i++)
{
if(s1[i]>='a'&&s1[i]<='z')
s1[i]-=32;
}
}
else
{
for(i=0;i<len;i++)
{
if(s1[i]>='A'&&s1[i]<='Z')
s1[i]+=32;
}
}
for(i=0;i<len;i++)
{
if(s1[i]==ch[0])
{
sum++;
}
}
printf("%.5lf\n",1.0*sum/len);
}
return 0;
}