int casegap='a'-'A'; #include<iostream> #include<iomanip> using namespace std; int main(){ char letter,word[200]; while(cin>>letter>>word){ if(letter==EOF) break; double frequency=0; int i=0; while(word[i]!='\0'){ if(word[i]==letter||word[i]==letter+casegap||word[i]==letter-casegap) frequency++; i++; } double probability=frequency/i; cout<<fixed<<setprecision(5)<<probability<<endl; } return 0; }