void extendEuclid(ll a, ll b){ if(b){ extendEuclid(b, a % b); ll x2 = x, y2 = y; x = y2; y = x2 - (a / b) * y2; }else{ x = 1ll; y = 0ll; d = a; } }
LL extendEuclid(LL a, LL b, LL &x, LL &y) { if (b == 0) { x = 1; y = 0; return a; } LL d = extendEuclid(b, a%b, y, x); y -= x*(a/b); return d; }