import java.io.*;
import java.util.*;

class Main {
    void solve(){
        Scanner sc = new Scanner( System.in );
        int m = sc.nextInt();
        int f = sc.nextInt();
        int b = sc.nextInt();
        if ( m + f >= b ) System.out.println( Math.max( 0, b - m ) );
        else System.out.println("NA");
     }
     public static void main( String[] a ) {new P02().solve(); }
}