class Dictionary:
    def __init__(self):
        self.keys = []
        self.vals = []
        
    def setVal(self, key, val):
        if key in self.keys:
            loc = (self.keys).index(key)
            self.vals[loc] = val
        else:
            self.keys.append(key)
            self.vals.append(val)

    def size(self):
        return len(self.keys)

    def __getitem__(self, key):
        if key in self.keys:
            loc = self.keys.index(key)
            return self.vals[loc]
        else:
            return None

    def remove(self, key):
        if key in self.keys:
            loc = self.keys.index(key)
            self.vals.pop(loc)
            self.keys.pop(loc)
            return
        else:
            return

    def __add__(self, other):
        new_dict = Dictionary()
        # Add keys from self
        for i in range(len(self.keys)):
            key = self.keys[i]
            value = self.vals[i]
            new_dict.setVal(key, value)
        # Add keys from other if they are not in self
        for i in range(len(other.keys)):
            key = other.keys[i]
            value = other.vals[i]
            if key not in self.keys:
                new_dict.setVal(key, value)
        return new_dict

    def __str__(self):
        result = ''
        for i in range(len(self.keys)):
            result += (str(self.keys[i]) + ':'
                          + str(self.vals[i]) + ', ')
        if result == '':
            return '{}'
        else:
            return '{' + result[:-2] + '}'