#include using namespace std; using ll = long long; using ld = long double; using ull = unsigned long long; using uint = unsigned; using pcc = pair; using pii = pair; using pll = pair; using pdd = pair; using tuplis = array; template using pq = priority_queue, greater>; const ll LINF=0x1fffffffffffffff; const ll MINF=0x7fffffffffff; const int INF=0x3fffffff; const int MOD=1000000007; const int MODD=998244353; const ld DINF=numeric_limits::infinity(); const ld EPS=1e-9; const ld PI=3.1415926535897932; const ll dx[] = {0, 1, 0, -1, 1, -1, 1, -1}; const ll dy[] = {1, 0, -1, 0, 1, 1, -1, -1}; #define overload4(_1,_2,_3,_4,name,...) name #define overload3(_1,_2,_3,name,...) name #define rep1(n) for(ll i=0;i(a);) #define rrep4(i,a,b,c) for(ll i=(a)+((b)-(a)-1)/(c)*(c);i>=(a);i-=c) #define rrep(...) overload4(__VA_ARGS__,rrep4,rrep3,rrep2,rrep1)(__VA_ARGS__) #define each1(i,a) for(auto&&i:a) #define each2(x,y,a) for(auto&&[x,y]:a) #define each3(x,y,z,a) for(auto&&[x,y,z]:a) #define each(...) overload4(__VA_ARGS__,each3,each2,each1)(__VA_ARGS__) #define all1(i) begin(i),end(i) #define all2(i,a) begin(i),begin(i)+a #define all3(i,a,b) begin(i)+a,begin(i)+b #define all(...) overload3(__VA_ARGS__,all3,all2,all1)(__VA_ARGS__) #define rall1(i) (i).rbegin(),(i).rend() #define rall2(i,k) (i).rbegin(),(i).rbegin()+k #define rall3(i,a,b) (i).rbegin()+a,(i).rbegin()+b #define rall(...) overload3(__VA_ARGS__,rall3,rall2,rall1)(__VA_ARGS__) #define sum(...) accumulate(all(__VA_ARGS__),0LL) #define dsum(...) accumulate(all(__VA_ARGS__),0.0L) #define Msum(...) accumulate(all(__VA_ARGS__),0_M) #define elif else if #define unless(a) if(!(a)) #define INT(...) int __VA_ARGS__;in(__VA_ARGS__) #define LL(...) ll __VA_ARGS__;in(__VA_ARGS__) #define ULL(...) ull __VA_ARGS__;in(__VA_ARGS__) #define STR(...) string __VA_ARGS__;in(__VA_ARGS__) #define CHR(...) char __VA_ARGS__;in(__VA_ARGS__) #define DBL(...) double __VA_ARGS__;in(__VA_ARGS__) #define LD(...) ld __VA_ARGS__;in(__VA_ARGS__) #define Sort(a) sort(all(a)) #define Rev(a) reverse(all(a)) #define Uniq(a) sort(all(a));a.erase(unique(all(a)),end(a)) #define vec(type,name,...) vectorname(__VA_ARGS__) #define VEC(type,name,size) vectorname(size);in(name) #define vv(type,name,h,...) vector>name(h,vector(__VA_ARGS__)) #define VV(type,name,h,w) vector>name(h,vector(w));in(name) #define vvv(type,name,h,w,...) vector>>name(h,vector>(w,vector(__VA_ARGS__))) template auto min(const T& a){ return *min_element(all(a)); } template auto max(const T& a){ return *max_element(all(a)); } inline ll popcnt(ull a){ return __builtin_popcountll(a); } ll gcd(ll a, ll b){ while(b){ ll c = b; b = a % b; a = c; } return a; } ll lcm(ll a, ll b){ if(!a || !b) return 0; return a * b / gcd(a, b); } ll intpow(ll a, ll b){ ll ans = 1; while(b){ if(b & 1) ans *= a; a *= a; b /= 2; } return ans; } ll modpow(ll a, ll b, ll p){ ll ans = 1; while(b){ if(b & 1) (ans *= a) %= p; (a *= a) %= p; b /= 2; } return ans; } template bool chmin(T& a, const T& b){ if(a > b){ a = b; return 1; } return 0; } template bool chmax(T& a, const T& b){ if(a < b){ a = b; return 1; } return 0; } template bool chmin(T& a, const U& b){ if(a > T(b)){ a = b; return 1; } return 0; } template bool chmax(T& a, const U& b){ if(a < T(b)){ a = b; return 1; } return 0; } vector iota(ll n){ vector a(n); iota(a.begin(), a.end(), 0); return a; } vector factor(ull x){ vector ans; for(ull i = 2; i * i <= x; i++) if(x % i == 0){ ans.push_back({i, 1}); while((x /= i) % i == 0) ans.back().second++; } if(x != 1) ans.push_back({x, 1}); return ans; } map factor_map(ull x){ map ans; for(ull i = 2; i * i <= x; i++) if(x % i == 0){ ans[i] = 1; while((x /= i) % i == 0) ans[i]++; } if(x != 1) ans[x] = 1; return ans; } vector divisor(ull x){ vector ans; for(ull i = 1; i * i <= x; i++) if(x % i == 0) ans.push_back(i); rrep(ans.size() - (ans.back() * ans.back() == x)) ans.push_back(x / ans[i]); return ans; } template unordered_map press(vector a){ Uniq(a); unordered_map ans; rep(a.size()) ans[a[i]] = i; return ans; } template map press_map(vector a){ Uniq(a); map ans; rep(a.size()) ans[a[i]] = i; return ans; } int scan(){ return getchar(); } void scan(int& a){ scanf("%d", &a); } void scan(unsigned& a){ scanf("%u", &a); } void scan(long& a){ scanf("%ld", &a); } void scan(long long& a){ scanf("%lld", &a); } void scan(unsigned long long& a){ scanf("%llu", &a); } void scan(char& a){ do{ a = getchar(); }while(a == ' ' || a == '\n'); } void scan(float& a){ scanf("%f", &a); } void scan(double& a){ scanf("%lf", &a); } void scan(long double& a){ scanf("%Lf", &a); } void scan(vector& a){ for(unsigned i = 0; i < a.size(); i++){ int b; scan(b); a[i] = b; } } void scan(char a[]){ scanf("%s", a); } void scan(string& a){ cin >> a; } template void scan(vector&); template void scan(array&); template void scan(pair&); template void scan(T(&)[size]); template void scan(vector& a){ for(auto&& i : a) scan(i); } template void scan(deque& a){ for(auto&& i : a) scan(i); } template void scan(array& a){ for(auto&& i : a) scan(i); } template void scan(pair& p){ scan(p.first); scan(p.second); } template void scan(T (&a)[size]){ for(auto&& i : a) scan(i); } template void scan(T& a){ cin >> a; } void in(){} template void in(Head& head, Tail&... tail){ scan(head); in(tail...); } void print(){ putchar(' '); } void print(bool a){ printf("%d", a); } void print(int a){ printf("%d", a); } void print(unsigned a){ printf("%u", a); } void print(long a){ printf("%ld", a); } void print(long long a){ printf("%lld", a); } void print(unsigned long long a){ printf("%llu", a); } void print(char a){ printf("%c", a); } void print(char a[]){ printf("%s", a); } void print(const char a[]){ printf("%s", a); } void print(float a){ printf("%.15f", a); } void print(double a){ printf("%.15f", a); } void print(long double a){ printf("%.15Lf", a); } void print(const string& a){ for(auto&& i : a) print(i); } template void print(const complex& a){ if(a.real() >= 0) print('+'); print(a.real()); if(a.imag() >= 0) print('+'); print(a.imag()); print('i'); } template void print(const vector&); template void print(const array&); template void print(const pair& p); template void print(const T (&)[size]); template void print(const vector& a){ if(a.empty()) return; print(a[0]); for(auto i = a.begin(); ++i != a.end(); ){ putchar(' '); print(*i); } } template void print(const deque& a){ if(a.empty()) return; print(a[0]); for(auto i = a.begin(); ++i != a.end(); ){ putchar(' '); print(*i); } } template void print(const array& a){ print(a[0]); for(auto i = a.begin(); ++i != a.end(); ){ putchar(' '); print(*i); } } template void print(const pair& p){ print(p.first); putchar(' '); print(p.second); } template void print(const T (&a)[size]){ print(a[0]); for(auto i = a; ++i != end(a); ){ putchar(' '); print(*i); } } template void print(const T& a){ cout << a; } int out(){ putchar('\n'); return 0; } template int out(const T& t){ print(t); putchar('\n'); return 0; } template int out(const Head& head, const Tail&... tail){ print(head); putchar(' '); out(tail...); return 0; } #ifdef DEBUG inline ll __lg(ull __n){ return sizeof(ull) * __CHAR_BIT__ - 1 - __builtin_clzll(__n); } #define debug(...) { print(#__VA_ARGS__); print(":"); out(__VA_ARGS__); } #else #define debug(...) void(0) #endif int First(bool i = true){ return out(i?"First":"Second"); } int Second(bool i = true){ return out("Second"); } int yes(bool i = true){ return out(i?"yes":"no"); } int Yes(bool i = true){ return out(i?"Yes":"No"); } int No(){ return out("No"); } int YES(bool i = true){ return out(i?"YES":"NO"); } int NO(){ return out("NO"); } int Yay(bool i = true){ return out(i?"Yay!":":("); } int possible(bool i = true){ return out(i?"possible":"impossible"); } int Possible(bool i = true){ return out(i?"Possible":"Impossible"); } int POSSIBLE(bool i = true){ return out(i?"POSSIBLE":"IMPOSSIBLE"); } void Case(ll i){ printf("Case #%lld: ", i); } template< typename T, bool isMin > struct ConvexHullTrickAddMonotone { #define F first #define S second using P = pair< T, T >; deque< P > H; ConvexHullTrickAddMonotone() = default; bool empty() const { return H.empty(); } void clear() { H.clear(); } inline int sgn(T x) { return x == 0 ? 0 : (x < 0 ? -1 : 1); } using D = long double; inline bool check(const P &a, const P &b, const P &c) { if(b.S == a.S || c.S == b.S) return sgn(b.F - a.F) * sgn(c.S - b.S) >= sgn(c.F - b.F) * sgn(b.S - a.S); //return (b.F-a.F)*(c.S-b.S) >= (b.S-a.S)*(c.F-b.F); return D(b.F - a.F) * sgn(c.S - b.S) / D(abs(ll(b.S - a.S))) >= D(c.F - b.F) * sgn(b.S - a.S) / D(abs(ll(c.S - b.S))); } void add(T a, T b) { if(!isMin) a *= -1, b *= -1; P line(a, b); if(empty()) { H.emplace_front(line); return; } if(H.front().F <= a) { if(H.front().F == a) { if(H.front().S <= b) return; H.pop_front(); } while(H.size() >= 2 && check(line, H.front(), H[1])) H.pop_front(); H.emplace_front(line); } else { assert(a <= H.back().F); if(H.back().F == a) { if(H.back().S <= b) return; H.pop_back(); } while(H.size() >= 2 && check(H[H.size() - 2], H.back(), line)) H.pop_back(); H.emplace_back(line); } } inline T get_y(const P &a, const T &x) { return a.F * x + a.S; } T query(T x) { assert(!empty()); int l = -1, r = H.size() - 1; while(l + 1 < r) { int m = (l + r) >> 1; if(get_y(H[m], x) >= get_y(H[m + 1], x)) l = m; else r = m; } if(isMin) return get_y(H[r], x); return -get_y(H[r], x); } T query_monotone_inc(T x) { assert(!empty()); while(H.size() >= 2 && get_y(H.front(), x) >= get_y(H[1], x)) H.pop_front(); if(isMin) return get_y(H.front(), x); return -get_y(H.front(), x); } T query_monotone_dec(T x) { assert(!empty()); while(H.size() >= 2 && get_y(H.back(), x) >= get_y(H[H.size() - 2], x)) H.pop_back(); if(isMin) return get_y(H.back(), x); return -get_y(H.back(), x); } #undef F #undef S }; using i128=__int128_t; signed main(){ LL(n,C); VEC(pll,a,n); vec(ll,dp1,n+1); vec(ll,dp2,n+1); dp1[0]=LINF; ConvexHullTrickAddMonotonecht1,cht2; rep(n){ const auto[A,B]=a[i]; cht1.add(-i,dp2[i]+C*i*(i+1)/2); dp1[i+1]=cht1.query(A+C*(i+1))+A*(i+1)+B+C*i*(i+1)/2; if(i){ cht2.add(a[i-1].first-C*i,dp1[i]-a[i-1].first*i+C*i*(i-1)/2); dp2[i+1]=min(dp1[i+1],(ll)cht2.query_monotone_inc(i+1)+C*(i+1)*(i+2)/2); } else dp2[i+1]=dp1[i+1]; } out(dp2[n]); }