class DirectedGraph:
    def __init__(self):
        self.graph = {}

    def add_node(self, node):
        """Add a node to the graph."""
        if node not in self.graph:
            self.graph[node] = []

    def add_edge(self, from_node, to_node):
        """Add a directed edge from 'from_node' to 'to_node'."""
        if from_node not in self.graph:
            self.add_node(from_node)
        if to_node not in self.graph:
            self.add_node(to_node)
        self.graph[from_node].append(to_node)

    def get_neighbors(self, node):
        """Return a list of neighbors (outgoing edges) for a given node."""
        if node not in self.graph:
            return []
        return self.graph[node]

    def get_no_incoming_nodes(self):
        """Return a list of nodes with no incoming edges."""
        all_nodes = set(self.graph.keys())
        nodes_with_incoming = set()
        
        for neighbors in self.graph.values():
            for neighbor in neighbors:
                nodes_with_incoming.add(neighbor)
        
        return sorted(list(all_nodes - nodes_with_incoming))

    def remove_node(self, node):
        """Remove a node and all edges connected to it (both incoming and outgoing)."""
        if node in self.graph:
            del self.graph[node]
        
        for key in list(self.graph.keys()):
            if node in self.graph[key]:
                self.graph[key].remove(node)

    def remove_edge(self, from_node, to_node):
        """Remove a directed edge from 'from_node' to 'to_node'."""
        if from_node in self.graph and to_node in self.graph[from_node]:
            self.graph[from_node].remove(to_node)

    def num_nodes(self):
        """Return the number of nodes in the graph."""
        return len(self.graph)

    def display(self):
        """Display the graph in an easy-to-read format."""
        for node, neighbors in self.graph.items():
            print(f"{node} -> {neighbors}")



# Example usage
if __name__ == "__main__":
    T = int(input())
    graph = []
    for i in range(T):
        chain = input()
        graph.append(chain)

g = DirectedGraph()
for chain in graph:
    g.add_node(chain[0])
    g.add_node(chain[1])
    g.add_edge(chain[0], chain[1])
    g.add_node(chain[2])
    g.add_edge(chain[1], chain[2])

try:
    output = ''
    while g.num_nodes() > 0:
        output += g.get_no_incoming_nodes()[0]
        g.remove_node(g.get_no_incoming_nodes()[0])
        # print(g.get_no_incoming_nodes())
        # g.display()
        # print()
    print(output)
except:
    print('SMTH WRONG')