hdu 2955 水题却wa几次值得反思

#include<iostream>
#include<cstring>
#include<algorithm>
#include<cstdio>
#include<vector>
#include<sstream>
#include<string>
#include<climits>
#include<stack>
#include<set>
#include<bitset>
#include<cmath>
#include<deque>
#include<map>
#include<queue>
#define iinf 0x7f7f7f7f
#define linf 1000000000000000000LL
#define dinf 1e200
#define eps 1e-11
#define all(v) (v).begin(),(v).end()
#define sz(x)  x.size()
#define pb push_back
#define mp make_pair
#define lng long long
#define sqr(a) ((a)*(a))
#define pii pair<int,int>
#define pll pair<lng,lng>
#define pss pair<string,string>
#define pdd pair<double,double>
#define X first
#define Y second
#define pi 3.14159265359
#define ff(i,xi,n) for(int i=xi;i<=(int)(n);++i)
#define ffd(i,xi,n) for(int i=xi;i>=(int)(n);--i)
#define ffl(i,r) for(int i=head[r];i!=-1;i=edge[i].next)
#define cc(i,j) memset(i,j,sizeof(i))
#define two(x)          ((lng)1<<(x))
#define lson l , mid , rt << 1
#define rson mid + 1 , r , rt << 1 | 1
#define mod  1000000007
#define pmod(x,y) (x%y+y)%y
using namespace std;
typedef vector<int>  vi;
typedef vector<string>  vs;
template<class T> inline void checkmax(T &x,T y){if(x<y) x=y;}
template<class T> inline void checkmin(T &x,T y){if(x>y) x=y;}
template<class T> inline T Min(T x,T y){return (x>y?y:x);}
template<class T> inline T Max(T x,T y){return (x<y?y:x);}
template<class T> T Abs(T a){return a>0?a:(-a);}
template<class T> inline T lowbit(T n){return (n^(n-1))&n;}
template<class T> inline int countbit(T n){return (n==0)?0:(1+countbit(n&(n-1)));}
int ncase,ans,n,m[111],sum[111];
double p[110],mxp,dp[11111];
int main()
{
    scanf("%d",&ncase);
    while(ncase--)
    {
        scanf("%lf%d",&mxp,&n);
        sum[0]=0;
        ff(i,1,n)
        {
            scanf("%d%lf",m+i,p+i);
            sum[i]=sum[i-1]+m[i];
        }
       ff(i,1,sum[n]) dp[i]=111;
        dp[0]=0.0;
        ff(i,1,n)
        {
            ffd(j,sum[i-1],0)
           checkmin(dp[j+m[i]],1-(1-dp[j])*(1-p[i]));
        }
        ans=0;
        for(int i=1;i<=sum[n];++i)
        if(dp[i]<=mxp) checkmax(ans,i);
        printf("%d\n",ans);
    }
    return 0;
}