#include<iostream>
using namespace std;

int main(){
	int l,m,n;
	int sum,month;
	bool flag = false;
	
	while(cin >> l,l){
		flag = false;
		month = 0;
		sum = 0;
		for(int i=0;i<12;i++){
			cin >> m >> n;
			sum += (m-n);
			if(sum > l && flag == false){
				month = i + 1;
				flag = true;
			}
		}
		
		if(!month)	cout << "NA" << endl;
		else	cout << month << endl;
	}
	return 0;
}