#include <iostream>
#include <queue>
#include <stack>
#include <vector>
#include <stdio.h>
#include <algorithm>
#include <string.h>
#include <string>
#include <cmath>
#include <complex>
#include <map>
using namespace std;

#define rep(i,n) for(int i=0;i<int(n);++i)
#define ALL(v) (v).begin(),(v).end()
#define PB push_back
#define EPS 1e-8
#define F first
#define S second

static const double PI=6*asin(0.5);
typedef pair<double,double> P;
typedef complex<double> CP;
typedef long long ll;

ll L,N,M;

int main(){
	while(cin>>L,L){
		bool f=true;
		rep(i,12){
			cin>>M>>N;
			L-=M-N;
			if(L<=0&&f){
				cout<<i+1<<endl;
				f=false;
			}
			else if(i==11&&f) cout<<"NA"<<endl;
		}
	}
	return 0;
}