t, m = map(int, input().split())
v = []
w = []
f = [[0 for _ in range(t+1)]for _ in range(m)]
for _ in range(m):
a,b = map(int, input().split())
v.append(a)
w.append(b)
for i in range(m):
for j in range(t+1):
f[i][j] = f[i-1][j]
if j >= v[i]:
f[i][j] = max(f[i][j], f[i-1][j-v[i]]+ w[i])
print(f[m-1][t])