#include<iostream>
#include<string>
#include<algorithm>
#include<map>
#include<set>
#include<utility>
#include<vector>
#include<cmath>
#include<cstring>
#include<cstdio>
#include<time.h>
#define loop(i,a,b) for(int i=a;i<b;i++) 
#define rep(i,a) loop(i,0,a)
#define pb push_back
#define mp make_pair
#define all(in) in.begin(),in.end()
const double PI=acos(-1);
const double EPS=1e-10;
using namespace std;
typedef long long ll;
typedef vector<int> vi;
int main(){
	int a;
	while(cin>>a,a){
		vector<int>sa(12);
		rep(i,12){
			int b,c;
			cin>>b>>c;
			sa[i]=b-c;
		}
		int sum=0;
		rep(i,12){
			sum+=sa[i];
			if(sum>=a){
				cout<<i+1<<endl;
				break;
			}
			if(i==11)cout<<"NA"<<endl;
		}
	}
}