#include<iostream> #include<cstring> using namespace std; int main(){ int p=0; string s; char c; while(cin>>c>>s){ p=0; for(int i=0;i<s.size();i++){ if(s[i]==c||s[i]-32==c||s[i]+32==c){ p++; } } double ans=double(p)/double(s.size())*1.0; printf("%.5lf",ans,"\n"); } return 0; }