#include<bits/stdc++.h>
using namespace std;
int main(){
	long long a,b,c;
	cin>>a>>b>>c;
	if(a+b==c){
	cout<<"plus"<<endl;
	}
	if(a-b==c){
	cout<<"minus"<<endl;
	}
	else{
	cout<<"illegal"<<endl;
	}
	return 0;
}