题解 | 小红的优惠券

#include <iostream>
using namespace std;
using ll = long long;
int main()
{
    ll n,m;
    cin>>n>>m;
    ll min = 1e5+1;//定义一个最小值
  ll  cost = n;//记录消费金额
    while(m--)
    {
        ll a,b;
        cin>>a>>b;
        if(a<=n){
            cost=n-b;
            if(cost<min){
                min = cost;
            }
        }
    }
    cout<< (min<n?min:n);
    return 0;
}