最远素数对AT_arc137_a [ARC137A] Coprime Pair

```cpp
#include<bits/stdc++.h>
    
using namespace std;
    
long long t;
const long long N = 2e5 + 10;
long long l,r;
    
void solve() {
    cin >> l >> r;
    for(long long i = r - l;i >= 0;i--) {
        for(long long j = l;j + i <= r;j++)
            if(__gcd(j,j + i) == 1) return (void)(cout << i);
    }
}
    
signed main() {
    ios::sync_with_stdio(0);
    cin.tie(0);cout.tie(0);
    t = 1;
    while(t--) solve();
    
    return 0;
}