N,Q = map(int,input().split())
L = []
for i in range(Q):
L.append(list(map(int,input().split())))
cnt = 0
for i in range(1,N+1):
for j in L:
if (i-j[0]) % j[1] ==0 and i-j[0] >=0:
break
else:
cnt+=1
print(cnt)