Toph - largest prime

#include<bits/stdc++.h>
using namespace std;
#define fast()(ios_base::sync_with_stdio(false),cin.tie(NULL));
bool res(int a)
{
    if(a==1)return false;
    for(int i=2;i<=sqrt(a);i++)
    {
        if(a%i==0)return false;
    }
    return true;
}
int main()
{
    int n;
    scanf("%d",&n);
    while(n--)
    {
        int x,y,i;
        scanf("%d %d",&x,&y);
        for( i=y;i>=x;i--)
        {
            if(res(i))
            {
                printf("%d\n",i);
                break;
            }
        }
        if(i==x-1)printf("-1\n");
    }
    return 0;
}