#include<iostream>
#include<string>
#include<cstring>
using namespace std;

#define MAX_N 100000
#define MAX_NUM 10

string S, T, U, V, pass;
int t[MAX_N + 1][3];
int u[MAX_N + 1][3];
int v[MAX_N + 1], cnt;
char W[MAX_NUM + 2] = "0123456789X";

int main() {
	while (cin >> S)
	{
		pass = "";
		T = ""; U = ""; V = "";
		memset(t, 0, sizeof(t));
		memset(u, 0, sizeof(u));
		memset(v, 0, sizeof(v));
		cnt = 0;
		S += ' ';
		for (int i = 0; i < S.size(); i++)
		{
			if (S[i] == '+')
			{
				T = pass;
				pass = "";
			}
			else if (S[i] == '=')
			{
				U = pass;
				pass = "";
			}
			else if (S[i] == ' ')
			{
				V = pass;
				pass = "";
			}
			else
			{
				pass += S[i];
			}
		}
		for (int i = 0; i < T.size(); i++)
		{
			for (int j = 0; j < MAX_NUM + 1; j++)
			{
				if (W[j] == T[i])
				{
					t[T.size() - 1 - i][0] = j;
				}
			}
		}
		for (int i = 0; i < U.size(); i++)
		{
			for (int j = 0; j < MAX_NUM + 1; j++)
			{
				if (W[j] == U[i])
				{
					t[U.size() - 1 - i][1] = j;
				}
			}
		}
		for (int i = 0; i < V.size(); i++)
		{
			for (int j = 0; j < MAX_NUM + 1; j++)
			{
				if (W[j] == V[i])
				{
					t[V.size() - 1 - i][2] = j;
				}
			}
		}
		for (int h = 0; h < MAX_NUM; h++)
		{
			if (h == 0)
			{
				if (V[0] == 'X' && V.size() >= 2)
				{
					goto F;
				}
				if (U[0] == 'X' && U.size() >= 2)
				{
					goto F;
				}
				if (T[0] == 'X' && T.size() >= 2)
				{
					goto F;
				}
			}
			for (int i = 0; i < MAX_N; i++)
			{
				for (int j = 0; j < 3; j++)
				{
					if (t[i][j] == MAX_NUM)
					{
						u[i][j] = h;
					}
					else {
						u[i][j] = t[i][j];
					}
				}
			}
			for (int i = 0; i < MAX_N; i++)
			{
				v[i] = 0;
			}
			for (int i = 0; i < MAX_N; i++)
			{
				v[i] += u[i][0] + u[i][1];
				if (v[i] >= MAX_NUM)
				{
					v[i] -= 10;
					v[i + 1]++;
				}
			}
			for (int i = 0; i < MAX_N; i++)
			{
				if ((u[i][2] != v[i]) || (u[i][2] == MAX_NUM && v[i] == h))
				{
					goto F;
				}
			}
			cout << h << endl;
			cnt++;
		F:;
		}
		if (cnt == 0)
		{
			cout << "NA" << endl;
		}
	}
}