#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>

using namespace std;

typedef long long ll;

ll n, m;

int main()
{
    scanf("%lld%lld", &n, &m);
    while(m --){
        ll ans = 0;
        ll l, r, rr;
        scanf("%lld%lld", &l, &r);
        for(ll i = l; i <= r; i = rr + 1){
            ans = max(ans, n - (n / i) * i);
            rr = n / (n / i);
        }
        printf("%lld\n", ans);
    }
    return 0;
}