poj Cash Machine

http://poj.org/problem?id=1276

 #include<cstdio>
 #include<cstring>
 #include<cmath>
 #include<algorithm>
 #define  For(n) for(int i=1; i<=(n); i++)
 #define maxn 100010
 using namespace std;
 
 int dp[maxn];
 struct node
 {
     int n;
     int m;
 }p[maxn];
 int cash,n;
 
 int main()
 {
     while(scanf("%d%d",&cash,&n)!=EOF)
     {
         For(n) scanf("%d%d",&p[i].n,&p[i].m);
         if(n==||cash==) {printf("0\n");continue;}
         int max1=;
         memset(dp,,sizeof(dp));
         dp[]=;
         for(int i=; i<=n; i++)
         {
             for(int j=max1; j>=; j--)
             {
                 if(dp[j])
                 {
                     for(int k=; k<=p[i].n; k++)
                     {
                         int sum=j+k*p[i].m;
                         if(sum>cash) break;
                         dp[sum]=;
                         max1=max(max1,sum);
                     }
                 }
             }
         }
         printf("%d\n",max1);
     }
     return ;
 }