N = 110
M = 1010
p = [0] * N
v = [0] * N
d = [[0] * M for i in range(N)]

C, n = map(int, input().split())

for i in range(1, n + 1):
    p[i], v[i] = map(int, input().split())

for i in range(1, n + 1):
    for j in range(1, C + 1):
        d[i][j] = d[i - 1][j]
        if j >=  p[i]:
            d[i][j] = max(d[i][j], d[i - 1][j - p[i]] + v[i])

print(d[n][C])