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(); } }