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