#pragma GCC optimize("Ofast")
#pragma GCC target("avx2")

#define rd(v) long v=0;{long _c;while(_c=*rp++-48,_c>=0)v=v*10+_c;}
#define wt(v) {ulong _z=v;do*--wp=_z%10+48;while(_z/=10);}
#define rep(v,e) for(long v=0;v<e;++v)
#define chmax(v,a) (v=v>=a?v:a)

typedef unsigned long ulong;

void radix_sort_aux(ulong*a,ulong*b,int n){
	int c[256];
	for(int i=0;i<256;++i){
		c[i]=0;
	}
	for(int i=0;i<n;++i){
		++c[a[i]&255];
	}
	int t=0;
	for(int i=256;i--;){
		int u=c[i];
		c[i]=t;
		t+=u;
	}
	for(int i=0;i<n;++i){
		b[c[a[i]&255]++]=a[i]>>8|a[i]<<56;
	}
}

void radix_sort(ulong*a,int n){
	static ulong b[5000];
	radix_sort_aux(a,b,n);
	radix_sort_aux(b,a,n);
	radix_sort_aux(a,b,n);
	radix_sort_aux(b,a,n);
}

ulong vw[5000];
long kp[5001];

void f1(long*np,long*mp){
	char*mmap();
	char*rp=mmap(0l,1l<<25,1,2,0,0ll);
	rd(n);
	rd(m);
	rep(i,n){
		rd(v);
		rd(w);
		vw[i]=v|w<<32;
	}
	radix_sort(vw,n);
	*np=n;
	*mp=m;
}

long f2(long n,long m){
	long z=0;
	rep(i,n){
		long v=vw[i]>>32;
		long w=(unsigned)vw[i];
		rep(j,m-w+1){
			chmax(kp[j],kp[j+w]+v);
		}
		chmax(z,kp[0]*v);
	}
	return z;
}

void f3(long z){
	char wbuf[64],*wp=wbuf+sizeof wbuf;
	wt(z);
	write(1,wp,wbuf+sizeof wbuf-wp);
	_exit(0);
}

int main(){
	long n,m;
	f1(&n,&m);
	f3(f2(n,m));
}