#include <bits/stdc++.h>
using namespace std;
int X[9]{1,2,3,4,5,6,7,8,9};
int main(){
	int T;
	cin>>T;
	for(int i=0;i<9;i++){
		if(X[i]*10+X[i]+X[i]==T){
			cout<<X[i];
			break;
		}else if(X[i]==9&&X[i]*10+X[i]+X[i]!=T){
			cout<<"404"<<endl;
		}
	}
	return 0;
}