hdu 1203 I NEED A OFFER!--01背包

/*
01背包问题
*/
#include<stdio.h>
double dp[10010],g[1010];
int m[1010],qian;
double p(double w,int i)
{
return 1-(1-w)*(1-dp[i]);
}
void zopack(int c,double w)
{
int i;
double gg;
for(i=qian;i>=c;i--)
{
gg=p(w,i-c);
dp[i]=gg>dp[i]?gg:dp[i];
}
}
int main()
{
int n,i;
while(scanf("%d%d",&qian,&n),n+qian)
{
for(i=0;i<n;i++)
scanf("%d%lf",&m[i],&g[i]);
for(i=0;i<=qian;i++)
dp[i]=0;
for(i=0;i<n;i++)
zopack(m[i],g[i]);
printf("%.1f%%\n",dp[qian]*100);
}
return 0;
}