#include<iostream>
using namespace std;
#include<string>
#include<vector>
string s1[10001], s2[10002];
vector<char>S1[10002], S2[10002];
int main()
{
	int n = 0,num=0;//记录原文行数,对的个数
	for (int i = 0;; i++)
	{
		getline(cin, s1[i]);
		if (s1[i] == "EOF")
		{
			n = i; break;
		}
	}
	for (int i = 0;; i++)
	{
		getline(cin, s2[i]);
		if (s2[i] == "EOF")break;
	}
	int t;
	cin >> t;
	for (int i = 0, j = 0; i < n; i++)
		for (;(j = s1[i].find('<')) != -1 && j < s1[i].length();j++)
		{
			if (j != 0)s1[i].erase(s1[i].begin()+j - 1, s1[i].begin()+j+1);//处理s1 <
			else if(j==0)s1[i].erase(s1[i].begin(),s1[i].begin()+1);
		}
	for (int i = 0,j=0; i < n; i++)
		for(;(j =s2[i].find('<'))!=-1&&j<s2[i].length();j++)
		{
			if (j != 0)s2[i].erase(s2[i].begin()+j-1, s2[i].begin()+j+1);//处理s2 <
			else if(j==0)s2[i].erase(s2[i].begin(), s2[i].begin()+1);
		}
	for (int i = 0; i < n; i++)
		for (int j = 0; j < s1[i].length()&&j<s2[i].length(); j++)
			if (s1[i][j] == s2[i][j])num++;
	cout << num*60.0 / t<< endl;
	system("pause");
	return 0;
}