I NEED A OFFER!

题目链接：https://vjudge.net/contest/395099#problem

#include <iostream>
#include <algorithm> 
#include <cstring>
using namespace std;

const int maxn = 1e5;

struct node
{
    int w;
    double val;
}arr[maxn];

double dp[maxn];

double getN(double a, double b)
{
    double t1 = 1 - a, t2 = 1 - b;
    return 1 - t1 * t2;
}

int main()
{
    int n, m;
    while (~scanf("%d %d", &n, &m))
    {
        if(n == 0 && m == 0) break;
        memset(dp, 0, sizeof(dp));
        for (int i = 1; i <= m; i++) scanf("%d %lf", &arr[i].w, &arr[i].val);
        for (int i = 1; i <= m; i++)
        {
            for (int j = n; j >= arr[i].w; j--)
            {
                dp[j] = max( getN(dp[j - arr[i].w], arr[i].val), dp[j]);
            }
        }
        printf("%.1f%%
", dp[n] * 100);
    }
    return 0;
}