HDU 1203 I NEED A OFFER!

#include<cstdio>
#include<cstring>
#include<cmath>
#include<algorithm>
using namespace std;

const int maxn=10000+10;
const int INF=0x7FFFFFFF;
int n,m;
int a[maxn];
double b[maxn];
double DP[maxn];

int main()
{
    int i,j;
    while(~scanf("%d%d",&n,&m))
    {
        if(n==0&&m==0) break;
        for(i=1; i<=m; i++)
        {
            scanf("%d%lf",&a[i],&b[i]);
            b[i]=1-b[i];
        }
        for(i=0; i<=n; i++) DP[i]=1;
        for(i=1; i<=m; i++)
            for(j=n; j-a[i]>=0; j--)
                DP[j]=fmin(DP[j],DP[j-a[i]]*b[i]);
        double MIN=INF;
        for(i=0; i<=n; i++)
            if(MIN>DP[i])
                MIN=DP[i];
        MIN=MIN*100;
        printf("%.1lf",100-MIN);
        printf("%%\n");
    }
    return 0;
}