#define ATCODER #define _USE_MATH_DEFINES #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include using namespace std; using ll = long long; using ld = long double; using pll = pair; using pdd = pair; //template using pq = priority_queue, greater>; #define FOR(i, a, b) for(ll i=(a); i<(b);i++) #define REP(i, n) for(ll i=0; i<(n);i++) #define ROF(i, a, b) for(ll i=(b-1); i>=(a);i--) #define PER(i, n) for(ll i=n-1; i>=0;i--) #define REPREP(i,j,a,b) for(ll i=0;i > #define VV2(type,n,m,val) vector< vector > val;val.resize(n);for(ll i;i #define VEC(type,n,val) vector val;val.resize(n) #define VL vector #define VVL vector< vector > #define VP vector< pair > #define SZ size() #define all(i) begin(i),end(i) #define SORT(i) sort(all(i)) #define BITI(i) (1<>i) & 1) != 0) #define ALLBIT(n) (ll(1)<v?v:n #define MP(a,b) make_pair(a,b) #define DET2(x1,y1,x2,y2) (x1)*(y2)-(x2)*(y1) #define DET3(x1,y1,z1,x2,y2,z2,x3,y3,z3) (x1)*(y2)*(z3)+(x2)*(y3)*(z1)+(x3)*(y1)*(z2)-(z1)*(y2)*(x3)-(z2)*(y3)*(x1)-(z3)*(y1)*(x2) #define INC(a) for(auto& v:a)v++; #define DEC(a) for(auto& v:a)v--; #define SQU(x) (x)*(x) #define L0 ll(0) #ifdef ATCODER #include using namespace atcoder; //using mint = modint1000000007; using mint2 = modint998244353; #endif template vector read(size_t n) { vector ts(n); for (size_t i = 0; i < n; i++) cin >> ts[i]; return ts; } template void read_tuple_impl(TV&) {} template void read_tuple_impl(TV& ts) { get(ts).emplace_back(*(istream_iterator(cin))); read_tuple_impl(ts); } template decltype(auto) read_tuple(size_t n) { tuple...> ts; for (size_t i = 0; i < n; i++) read_tuple_impl(ts); return ts; } using val = ll; using func = ll; val op(val a, val b) { return a + b; } val e() { return 0; } val mp(func f, val a) { return a + f; } func comp(func f, func g) { return f + g; } func id() { return 0; } ll g; bool f(val a) { return a < g; } ll di[4] = { 1,0,-1,0 }; ll dj[4] = { 0,1,0,-1 }; ll si[4] = { 0,3,3,0 }; ll sj[4] = { 0,0,3,3 }; //ll di[4] = { -1,-1,1,1 }; //ll dj[4] = { -1,1,-1,1 }; //ll di8[8] = { 0,-1,-1,-1,0,1,1,1 }; //ll dj8[8] = { -1,-1,0,1,1,1,0,-1 }; void solve() { ll x, n; cin >> x >> n; ll l = 0, r = 2e9; while (l + 1 < r) { ll m = (l + r) / 2; ll s = m * (m + 1) / 2; if (abs(x) < s) { r = m; } else { l = m; } } if (n <= l) { if (x < 0) { x += n * (n + 1) / 2; } else { x -= n * (n + 1) / 2; } cout << x; return; } if (x < 0) { x += l * (l + 1) / 2; } else { x -= l * (l + 1) / 2; } if (x <= 0) { if ((n - l) % 2) { cout << x + r + (n - l) / 2; } else { cout << x - (n - l) / 2; } } else { if ((n - l) % 2) { cout << x - r - (n - l) / 2; } else { cout << x + (n - l) / 2; } } return; } int main() { ll t = 1; //cin >> t; while (t--) { solve(); } return 0; }