B"Let's call an array consisting of n integer numbers a1, a2, ..., an, beautiful if it has the following property: Sereja wants to build a beautiful array a, consisting of n integers. But not everything is so easy, Sereja's friend Dima has m coupons, each contains two integers qi, xe2 x80 x89wi. Coupon i costs wi and allows you to use as many numbers qi as you want when constructing the array a. Values qi are distinct. Sereja has no coupons, so Dima and Sereja have made the following deal. Dima builds some beautiful array a of n elements. After that he takes wi rubles from Sereja for each qi, which occurs in the array a. Sereja believed his friend and agreed to the contract, and now he is wondering, what is the maximum amount of money he can pay. Help Sereja, find the maximum amount of money he can pay to Dima. The first line contains two integers n and m (1 xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89n xe2 x80 x89 xe2 x89 xa4 xe2 x80 x892 xc2 xb7106, xe2 x80 x891 xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89m xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89105). Next m lines contain pairs of integers. The i-th line contains numbers qi, xe2 x80 x89wi (1 xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89qi, xe2 x80 x89wi xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89105). It is guaranteed that all qi are distinct. In a single line print maximum amount of money (in rubles) Sereja can pay. Please, do not use the %lld specifier to read or write 64-bit integers in xd0 xa1++. It is preferred to use the cin, cout streams or the %I64d specifier. In the first sample Sereja can pay 5 rubles, for example, if Dima constructs the following array: [1, xe2 x80 x892, xe2 x80 x891, xe2 x80 x892, xe2 x80 x892]. There are another optimal arrays for this test. In the third sample Sereja can pay 100 rubles, if Dima constructs the following array: [2]."...