import std.algorithm;
import std.array;
import std.ascii;
import std.bigint;
import std.complex;
import std.container;
import std.conv;
import std.functional;
import std.math;
import std.range;
import std.stdio;
import std.string;
import std.typecons;
 
auto readInts() {
    return array(map!(to!int)(readln().strip().split()));
}
auto readInt() {
    return readInts()[0];
}
auto readLongs() {
    return array(map!(to!long)(readln().strip().split()));
}
auto readLong() {
    return readLongs()[0];
}
 
void readlnTo(T...)(ref T t) {
    auto s = readln().split();
    assert(s.length == t.length);
    foreach(ref ti; t) {
        ti = s[0].to!(typeof(ti));
        s = s[1..$];
    }
}
 
const real eps = 1e-10;
 
const long p = 1_000_000_000 + 7;
 
long solve(string l) {
    long[string] memo;
    auto q = heapify!("a > b")([tuple(0L, l)]);
    while(!q.empty()) {
        auto t = q.front();
        q.popFront();
        auto s = t[1];
        if(s in memo) {
            continue;
        }
        auto v = t[0];
        if(s.uniq.count == 1) {
            return v;
        }
        memo[s] = v;
        foreach(i; iota(s.length-1)) {
            if(s[i] != s[i+1]) {
            }
        }
    }
    return -1;
}
 
void main(){
    while(true) {
        auto l = readln.strip();
        if(l == "0") {
            return;
        }
        auto ans = solve(l);
        writeln(ans >= 0 ? ans.to!string: "NA");
    }
}