C++ :

#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
int n,a,b;
struct _{int a,b;}__[10003];
bool pp(_ a,_ b){return a.b*a.a<b.b*b.a;};
struct big{
	int n;
	int a[16003];
	void operator*=(int b){
		for(int i=0;i<n;++i)
		a[i]*=b;
		for(int i=0;i<n;++i)
		if(a[i]>9){
			a[i+1]+=a[i]/10;
			a[i]%=10;
		}
		while(a[n]>9){
			a[n+1]=a[n]/10;
			a[n]%=10;
			++n;
		}
		if(a[n])++n;
	}
	bool operator>(big b){
		if(n!=b.n)
		return n>b.n?1:0;
		for(int i=n-1;i>=0;++i)
		if(a[i]!=b.a[i])
		return a[i]>b.a[i]?1:0;
		return 0;
	}
	big operator/(int b){
		bool flag=0;
		big res;
		memset(res.a,0,sizeof res.a);
		res.n=0;
		int now=0;
		for(int i=n-1;i>=0;--i){
			now=now*10+a[i];
			if(now>=b){
				if(!flag)
				res.n=i+1,flag=1;
				res.a[i]=now/b;
				now%=b;
			}
		}
		return res;
	}
}now,ans;
int main(){
	scanf("%d%d%d",&n,&a,&b);
	for(int i=0;i<n;++i)
	scanf("%d%d",&__[i].a,&__[i].b);
	sort(__,__+n,pp);
	while(a){
		now.a[now.n++]=a%10;
		a/=10;
	}
	for(int i=0;i<n;++i){
		big stay=now/__[i].b;
		ans=ans>stay?ans:stay;
		now*=__[i].a;
	}
	for(int i=ans.n-1;i>=0;--i)
	printf("%d",ans.a[i]);
	return 0;
}