题解 | 小红的优惠券

price , discount =map(int,input().split())
discount_detail ={}
for i in range(1,discount+1):
    toatl1 , sub1 = map(int,input().split())
    discount_detail[toatl1] =sub1
    i = i+1
list_price=[]
for k , v in  discount_detail.items():
    if(k <= price ):
        sum = price-v
        list_price.append(sum)
    else:
        continue
list_price.append(price)
list_price.sort()
print(list_price[0])