---------- A rectangular cake is transported via a truck to a restaurant. On the way to the destination, the truck hits a pothole, which shatters the cake in $N$ perfectly rectangular pieces of width $w_i$ and length $l_i$, for $1 \le i \le N$. At the destination, the damage is assessed, and the customer decides to order a replacement cake of the same dimensions. Unfortunately, the original order form was incompletely filled and only the width $W$ of the cake is known. The restaurant asks for your help to find out the length $L$ of the cake. Fortunately, all pieces of the cake have been kept. # Input The input consists of the following integers: - on the first line, the width $W$ of the cake; - on the second line, the number $N$ of shattered pieces; - on each of the next $N$ lines, the width $w_i$ and length $l_i$ of each piece. $$1 \le N \le 5000000$$ $$1 \le W, L \le 10000$$ $$1 \le w_i, l_i \le 10000$$ # Output The output should be the integer $L$. ## Sample Input ``` 4 7 2 3 1 4 1 2 1 2 2 2 2 2 2 1 ``` ## Sample Output ``` 6 ```