#include <bits/stdc++.h>

using namespace std;

#define fr(a,b,c) for(int a=b; a<c; a++)
#define sc(a) scanf("%d",&a)
#define sc2(a,b) scanf("%d %d",&a,&b)
#define ll long long
typedef vector<int> vi;
typedef vector <vi> vii;



int v[350];

int main()
{
    int tc;
    sc(tc);
    while(tc--){
        int m,a,maximo=0;
        sc2(m,a);
        m = m*100;
        fr(i,0,a){
            int d,f;
            scanf("%d",&d);
            char aux;
            scanf("%c",&aux);
            if(aux =='.'){
                scanf("%d",&f);
            }
            else f=0;
            d = d*100 +f;
            int div = m/d;
            maximo = max(maximo,m-div*d);
        }
        printf("%d.%.2d\n",maximo/100,maximo%100);
    }
    return 0;
}