nuj

#include <bits/stdc++.h>
using namespace std;
const string fname("text.");
ifstream fin(fname + "in");
ofstream fout(fname + "out");
///************************
void finish(), procIfElse(), exePrint(), executeFunction();
bool setVar(), createVar();
#define ERR_FUN fout << "ERROR" << endl; return;
string ans, s;
unordered_map<string, string> variables;
bool errInCurrFn = false, retInCurrFn = false;

void exePrint() {
    fin >> s;
    if (variables.count(s)) {
        ans += variables[s];
    } else {
        ans += s;
    }
}

void finish() {
    fout << ans << endl;
}

void procIfElse() {
    unordered_map<string, int> st;
    fin >> s;//if cond
    st["if"]++;
    if (variables.count(s) && s != "true" && s != "false") {
        if (variables[s] == "true" || variables[s] == "false") {
            s = variables[s];
        } else {
            errInCurrFn = true;
        }
    }
    if (s == "true") {
        while (fin >> s && s != "end") {
            if (s == "if") {
                procIfElse();
            } else if (s == "var") {
                if (!createVar()) {
                    errInCurrFn = true;
                }
            } else if (s == "set") {
                if (!setVar()) {
                    errInCurrFn = true;
                }
            } else if (s == "print") {
                exePrint();
            } else if (s == "return") {
                retInCurrFn = true;
                return;
            }
        }
        st["if"]--;
        fin >> s;//else
        while (fin >> s && st["if"] >= 0) {
            if (s == "if") st["if"]++;
            if (s == "else") st["if"]++;
            if (s == "end") {
                st["if"]--;
            }
        }
    } else {
        while (st["else"] >= 0 && fin >> s) {
            if (s == "else") st["else"]++;
            if (s == "end") {
                st["else"]--;
            }
        }
        while (fin >> s && s != "end") {
            if (s == "var") {
                if (!createVar()) {
                    errInCurrFn = true;
                }
            }
            else if (s == "set") {
                if (!setVar()) {
                    errInCurrFn = true;
                }
            }
            else if (s == "print") {
                exePrint();
            }
            else if (s == "return") {
                retInCurrFn = true;
                return;
            }
            else if (s == "if") {
                procIfElse();
            }
        }
    }
}

bool createVar() {
    string name, val;
    fin >> name >> val;
    if (variables.count(name)) {
        return false;
    }
    if (variables.count(val)) {
        variables[name] = variables[val];
    } else {
        variables[name] = val;
    }
    return true;
}

bool setVar() {
    string name, val;
    fin >> name >> val;
    if (!variables.count(name)) {
        return false;
    }
    if (variables.count(val)) {
        variables[name] = variables[val];
    } else {
        variables[name] = val;
    }
    return true;
}


void executeFunction() {
    ans = "";
    variables.clear();
    errInCurrFn = false;
    retInCurrFn = false;
    //cerr << "HERE" << endl;
    while (fin >> s) {
        if (retInCurrFn) {
            if (s == "start") {
                finish();
                return;
            }
            continue;
        }
        if (s == "print") exePrint();
        else if (s == "var") {
            if (!createVar()) {
                errInCurrFn = true;
            }
        }
        else if (s == "set") {
            if (!setVar()) {
                errInCurrFn = true;
            }
        }
        else if (s == "end") {
            break;
        }
        else if (s == "if") {
            procIfElse();
        } else if (s == "return" || retInCurrFn) {
            while (fin >> s && s != "start");
        }
    }
    if (errInCurrFn) {
        ans = "";
        variables.clear();
        errInCurrFn = false;
        ERR_FUN
    }
    finish();
}

int main() {
    int n;
    fin >> n;
    while (s == "start" || fin >> s) {
        if (s == "start") {
            executeFunction();
        }
    }
    return 0;
}