#include <bits/stdc++.h> using namespace std; int main() { int i; float s; char a[200],b; while (scanf("%c %s",b,a)!=EOF) { i=s=0; while (i<strlen(a)) { if (a[i]+32==b or a[i]-32==b or a[i]==b) s++; i++; } printf("%.5f\n",1.0*s/strlen(a)); } return 0; }