# include <bits/stdc++.h>
using namespace std;
using LL = long long;
using ULL = unsigned long long;
const double PI = acos(-1);
template<class T>constexpr T INF() { return ::std::numeric_limits<T>::max(); }
template<class T>constexpr T HINF() { return INF<T>() / 2; }
template <typename T_char>T_char TL(T_char cX) { return tolower(cX); };
template <typename T_char>T_char TU(T_char cX) { return toupper(cX); };
template<typename T>vector<T> make_v(size_t a){ return vector<T>(a); }
template<typename T,typename... Ts>auto make_v(size_t a, Ts... ts){ return vector<decltype(make_v<T>(ts...))>(a,make_v<T>(ts...)); }
template<typename T,typename V>typename enable_if<is_class<T>::value==0>::type fill_v(T &t, const V &v){ t = v; }
template<typename T,typename V>typename enable_if<is_class<T>::value!=0>::type fill_v(T &t, const V &v){ for(auto &e : t) fill_v(e, v); }
const int vy[] = { -1, -1, -1, 0, 1, 1, 1, 0 }, vx[] = { -1, 0, 1, 1, 1, 0, -1, -1 };
const int dx[4] = { 0,1,0,-1 }, dy[4] = { 1,0,-1,0 };
int popcnt(unsigned long long n) { int cnt = 0; for (int i = 0; i < 64; i++)if ((n >> i) & 1)cnt++; return cnt; }
int d_sum(LL n) { int ret = 0; while (n > 0) { ret += n % 10; n /= 10; }return ret; }
int d_cnt(LL n) { int ret = 0; while (n > 0) { ret++; n /= 10; }return ret; }
LL gcd(LL a, LL b) { if (b == 0)return a; return gcd(b, a%b); };
LL lcm(LL a, LL b) { LL g = gcd(a, b); return a / g*b; };
# define ALL(qpqpq)           (qpqpq).begin(),(qpqpq).end()
# define UNIQUE(wpwpw)        sort(ALL((wpwpw)));(wpwpw).erase(unique(ALL((wpwpw))),(wpwpw).end())
# define LOWER(epepe)         transform(ALL((epepe)),(epepe).begin(),TL<char>)
# define UPPER(rprpr)         transform(ALL((rprpr)),(rprpr).begin(),TU<char>)
# define FOR(i,tptpt,ypypy)   for(LL i=(tptpt);i<(ypypy);i++)
# define REP(i,upupu)         FOR(i,0,upupu)
# define INIT                 std::ios::sync_with_stdio(false);std::cin.tie(0)

string s;
char c;

bool isLower(char x){
    if('a' <= x && x <= 'z')return true;
    return false;
}

char toUpper(char x){
    return (char)(x - 32);
}

char toLower(char x){
    return (char)(x + 32);
}

string fL(string t){
    string ret = "";
    REP(i, (int)t.size()){
        if(0 < i && t[i - 1] == '_'){
            ret = ret + toUpper(t[i]);
        }
        else if(t[i] != '_')ret = ret + t[i];
    }
    if(!isLower(ret[0])){
        ret[0] = tolower(ret[0]);
    }
    return ret;
}

string fU(string t){
    string ret = "";
    REP(i, (int)t.size()){
        if(0 < i && t[i - 1] == '_'){
            ret = ret + toUpper(t[i]);
        }
        else if(t[i] != '_')ret = ret + t[i];
    }
    if(isLower(ret[0])){
        ret[0] = toUpper(ret[0]);
    }
    return ret;
}

string fD(string t){
    string ret = "";
    if(!isLower(t[0])){
        t[0] = tolower(t[0]);
    }
    REP(i, (int)t.size()){
        if(!isLower((char)(t[i]))){
            ret = ret + (string)("_");
            if(!isLower(t[i])){
                t[i] = toLower(t[i]);
            }
        }
        ret = ret + t[i];
    }
    if(!isLower(ret[0])){
        ret[0] = tolower(ret[0]);
    }
    return ret;
}

int main(){
    while(cin >> s >> c && c != 'X'){
        if(c == 'U'){
            cout << fU(s) << endl;
        }else if(c == 'L'){
            cout << fL(s) << endl;
        }else{
            bool flg = false;
            REP(i, (int)s.size()){
                if(s[i] == '_'){
                    flg = true;
                }
            }
            if(flg)cout << s << endl;
            else cout << fD(s) << endl;
        }
    }
}


Measured memory_bytes: 3148