#include "bits/stdc++.h"
using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
#define rep(i,n) for(ll i=0;i<(ll)(n);i++)
#define all(a)  (a).begin(),(a).end()
#define pb push_back
#define INF 999999999

vector<string> split(string s,char ch){
    vector<string> ret;
    string tmp ="";
    rep(i,s.size()){
        if(s[i]==ch){
            ret.pb(tmp);
            tmp = "";
        }else tmp+=s[i];
    }
    if(tmp.size())ret.pb(tmp);
    return ret;
}

bool is(string s){
    rep(i,s.size())if(s[i]=='+')s[i]='=';
    vector<string> res = split(s,'=');
    rep(i,res.size()){
        if(res[i].size()>=2&&res[i][0]=='0')return false;
    }
    int num[10];
    rep(i,3)num[i] = stoi(res[i]);
    if(num[0]+num[1]==num[2])return true;
    return false;
}

int main(){
    string s;
    while(cin>>s){
        rep(i,10){
            string tmp = s;
            rep(j,tmp.size())if(tmp[j]=='X')tmp[j]='0'+i;
            if(is(tmp)){
                cout<<i<<endl;
                break;
            }
            if(i==9)cout<<"NA"<<endl;
        }
    }
}