#include<bits/stdc++.h>
#include<fstream>
using namespace std;
ifstream fin("bac.txt");
int v[1001];
int main()
{int x,ok=1,r=-1,i,p;
while(fin>>x)
    v[x]=1;
i=0;
while(v[i]==0)
    i++;
p=i;
for(i=i+1;i<=1000;i++)
    {if(v[i]==1)
     {
     if(r<0)
       r=i-p;
      else
        if(i-p!=r)
           ok=0;
     p=i;}
     }
if(ok)
    cout<<"Ratie= "<<r;
else
    cout<<"NU";



}