#include <bits/stdc++.h>
using namespace std;
int main(){
	int m,f,b;
	cin >> m >> f >> b;
	if(f>=b-m){
		if(b-m>0){
			cout << b-m << endl;
		}
		else{
			cout << 0 << endl;
		}
	}
	else{
		cout << "NA" << endl;
	}
}
