include <bits/stdc++.h>//直接AC;

using namespace std; int u[100001],u1[100001]; struct l{

char x1[21];
int x2[21];

}x[10001]; bool cmp(l a,l b){

int t=0,m=0;
memset(u,0,sizeof(u));
memset(u1,0,sizeof(u1));
int minn=0;
minn=min(strlen(a.x1),strlen(b.x1));
for(int i=0;i<minn;i++){
	if(a.x2[i]!=b.x2[i]){
		return a.x2[i]>b.x2[i];
	}
}
	for(int j=0;j<strlen(a.x1);j++){
		u[++t]=a.x2[j];
				}
			for(int j=0;j<strlen(b.x1);j++){
		u[++t]=b.x2[j];
		}
	
			for(int j=0;j<strlen(b.x1);j++){
		u1[++m]=b.x2[j];
		}	
		for(int j=0;j<strlen(a.x1);j++){
		u1[++m]=a.x2[j];
				}
		for(int j=1;j<=m+t;j++){
				if(u[j]!=u1[j]){
		return  u[j]>u1[j];
	}
		}

} int main(){

int s;
cin>>s;
for(int i=1;i<=s;i++){
	scanf("%s",x[i].x1);
	for(int j=0;j<strlen(x[i].x1);j++){
		x[i].x2[j]=x[i].x1[j]-'0';
	}
}
sort(x+1,x+s+1,cmp);
for(int i=1;i<=s;i++){
	cout<<x[i].x1;
}
return 0;

}