use std::collections::HashSet;

fn main() {
    let mut ps = HashSet::new();
    let mut hs = HashSet::new();
    let N = 500000u64;
    for n in 1..N { hs.insert(n*(2*n-1)); }
    for n in 1..N { ps.insert(n*(3*n -1)/2 ); }
    for n in 286u64..N {
        let tn = n * (n+1)/2;
        if !hs.contains(&tn) { continue; }
        if !ps.contains(&tn) { continue; }
        println!("{}", tn);
        break;
    }
}