[USACO09OCT]津贴Allowance[贪心]

#include<cstdio>
#include<algorithm>
#define in inline
#define re register
#define int long long
using namespace std;
in int read()
{
	int s(0),b(0);char ch;
	do{ch=getchar();if(ch=='-')b=1;}while(ch<'0'||ch>'9');
	while(ch>='0'&&ch<='9') s=(s<<3)+(s<<1)+(ch^48),ch=getchar();
	if(b)return -s;return s;
}
struct node{int v,cnt;bool operator<(const node&t)const{return v<t.v;}}a[25];
int n,c,ans;
signed main()
{
	n=read(),c=read();
	int cc=0;
	for(re int i=1;i<=n;++i)
	{
		a[++cc].v=read(),a[cc].cnt=read();
		if(a[cc].v>=c) ans+=a[cc].cnt,--cc;
	}
	n=cc;
	sort(a+1,a+n+1);
	while(1)
	{
		cc=c;
		for(re int i=n;i>=1;--i)
			while(a[i].cnt&&a[i].v<=cc) cc-=a[i].v,--a[i].cnt;
		if(cc>0)
			for(re int i=1;i<=n;++i)
				while(a[i].cnt&&cc>0) cc-=a[i].v,--a[i].cnt;
		if(cc<=0) ++ans;
		else break;
	}
	printf("%lld\n",ans);
	return 0;
}