static int howManyAgentsToAdd(int noOfCurrentAgents, int[][] callsTimes) {
    if(callsTimes == null || callTimes.length == 0) return 0;
    int n = callsTime.length;
    int[] start = new int[n];
    int[] end = new int[n];

    for(int i=0;i<n;i++) {
        start[i] = callsTimes[i][0];
        end[i] = callsTimes[i][1];
    }

    int ans = maxOverlapIntervalCount( start, end );
    return Math.max(0, ans-noOfCurrentAgents);
}
public static int maxOverlapIntervalCount(int[] start, int[] end){
	int maxOverlap = 0;
	int currentOverlap = 0;

	Arrays.sort(start);
	Arrays.sort(end);

	int i = 0;
	int j = 0;
	int m=start.length,n=end.length;
	while(i< m && j < n){
		if(start[i] < end[j]){
			currentOverlap++;
			maxOverlap = Math.max(maxOverlap, currentOverlap);
			i++;
		}
		else{
			currentOverlap--;
			j++;
		}
	}

	return maxOverlap;
}