class TimeMap {

      Map<String,Map<Integer,String>> map;

    /** Initialize your data structure here. */
    public TimeMap( ) {
     this.map= new HashMap<>();
    }

    public void set(String key, String value, int timestamp) {
        map.putIfAbsent(key,new HashMap<Integer,String>());
        Map<Integer,String> internalMap= map.get(key);
        internalMap.put(timestamp,value);

    }

    public String get(String key, int timestamp) {


       if(!map.containsKey(key)){
           return "";
       }
        Map<Integer,String> internalMap = map.get(key);
        while(timestamp > 0 && !internalMap.containsKey(timestamp)){
            timestamp--;
        }
        if(timestamp==0){
            return "";
        }else{
            return internalMap.get(timestamp);
        }


    }
}
/**
 * Your TimeMap object will be instantiated and called as such:
 * TimeMap obj = new TimeMap();
 * obj.set(key,value,timestamp);
 * String param_2 = obj.get(key,timestamp);
 */