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;
}