#include<iostream>

#include<string>

using namespace std;

int main()

{

    string s;

    int a = ,b = ;

    cin >> s;

    for(int i = ;i < s.size();i++)

    {

        if(s[i] == 'L') a++;

        else if(s[i] == 'R')    a--;

        else if(s[i] == 'U')    b++;

        else if(s[i] == 'D')    b--;

    }

    a = a>?a:-a;

    b = b>?b:-b;

    if((a+b)%) cout << - << endl;

    else    cout << (a+b)/ <<  endl;

    return ;

}