class Queue:
    def __init__(self,size=0):
        self.__data = []
        self.__size=size
    def push(self,element):
        self.__data.insert(0,element)
    def getFirst(self):
        return self.__data[-1]
    def getLast(self):
        return self.__data[0]
    def pop(self):
        return self.__data.pop()
    def isEmpty(self):
        return not len(self.__data)
    def qPrint(self):
        print(self.__data)
    def isFull(self):
        if self.__size!=0:
            return len(self.__data)>=self.__size
        else:
            return False
class Package:
    def __init__(self, arrive,duration):
        self.__arrive=arrive
        self.__duration=duration
    def getArrive(self):
        return self.__arrive
    def getDuration(self):
        return self.__duration
size,n=list(map(int,input().split()))
buffer=Queue(size)
abstime=0
for i in range(n):
    inpack = Package(*list(map(int, input().split())))

    start=inpack.getArrive()
    duration=inpack.getDuration()
    if abstime < start and not buffer.isFull():
        abstime = start
    if not buffer.isFull():
        print(abstime)
        buffer.push(inpack)
        abstime += duration
    elif(buffer.getFirst().getDuration()-(start-buffer.getFirst().getArrive())<=0):
        buffer.pop()
        if abstime < start:
            abstime = start
        print(abstime)
        buffer.push(inpack)
        abstime += duration
    else:
        print(-1)