#include <iostream>
#include <cstdio>
#include <string>
#include <vector>
#include <map>
#include <algorithm>
#include <sstream>

#define mp make_pair
#define rep(i,n) for(int i = 0 ; i < n ; i++)
#define ll long long

using namespace std;

int main(){
	int l;
	while( cin >> l , l)
	{
		int money=0 , i , ans=0;
		for( i = 0; i<12; i++)  
		{
			int n , m;
			cin >> m >> n;
			money += m-n;
			if( l < money ) {
				ans = i+1;
				l = 100000000;
			}
		}
		if( ans ) cout << ans;
		else cout << "NA";
		puts("");
	}
	return 0;
}