// need #include #include // data structure #include #include #include #include #include #include #include #include //#include //#include //#include //#include #include // stream //#include //#include //#include //#include // etc #include #include #include #include #include #include #include // input #define INIT std::ios::sync_with_stdio(false);std::cin.tie(0); #define VAR(type, ...)type __VA_ARGS__;MACRO_VAR_Scan(__VA_ARGS__); template void MACRO_VAR_Scan(T& t) { std::cin >> t; } templatevoid MACRO_VAR_Scan(First& first, Rest&...rest) { std::cin >> first; MACRO_VAR_Scan(rest...); } #define VEC_ROW(type, n, ...)std::vector __VA_ARGS__;MACRO_VEC_ROW_Init(n, __VA_ARGS__); for(int i=0; i void MACRO_VEC_ROW_Init(int n, T& t) { t.resize(n); } templatevoid MACRO_VEC_ROW_Init(int n, First& first, Rest&...rest) { first.resize(n); MACRO_VEC_ROW_Init(n, rest...); } template void MACRO_VEC_ROW_Scan(int p, T& t) { std::cin >> t[p]; } templatevoid MACRO_VEC_ROW_Scan(int p, First& first, Rest&...rest) { std::cin >> first[p]; MACRO_VEC_ROW_Scan(p, rest...); } #define VEC(type, c, n) std::vector c(n);for(auto& i:c)std::cin>>i; #define MAT(type, c, m, n) std::vector> c(m, std::vector(n));for(auto& r:c)for(auto& i:r)std::cin>>i; // output #define OUT(d) std::cout<=(a);--i) #define REP(i, n) for(int i=0;i=0;--i) #define FORLL(i, a, b) for(ll i=ll(a);i=ll(a);--i) #define REPLL(i, n) for(ll i=0;i=0;--i) #define IN(a, x, b) (a<=x && x inline T CHMAX(T& a, const T b) { return a = (a < b) ? b : a; } template inline T CHMIN(T& a, const T b) { return a = (a > b) ? b : a; } #define EXCEPTION(msg) throw std::string("Exception : " msg " [ in ") + __func__ + " : " + std::to_string(__LINE__) + " lines ]" #define TRY(cond, msg) try {if (cond) EXCEPTION(msg);}catch (std::string s) {std::cerr << s << std::endl;} void CHECKTIME(std::function f) { auto start = std::chrono::system_clock::now(); f(); auto end = std::chrono::system_clock::now(); auto res = std::chrono::duration_cast((end - start)).count(); std::cerr << "[Time:" << res << "ns (" << res / (1.0e9) << "s)]\n"; } // test template std::vector> VV(int n) { return std::vector>(n); } template std::vector> VV(int n, int m, T init = T()) { return std::vector>(n, std::vector(m, init)); } template std::ostream& operator<<(std::ostream& os, std::pair p) { os << "(" << p.first << ", " << p.second << ")"; return os; } // type/const #define int ll using ll = long long; using ull = unsigned long long; using ld = long double; using PAIR = std::pair; using PAIRLL = std::pair; constexpr int INFINT = 1 << 30; // 1.07x10^ 9 constexpr int INFINT_LIM = (1LL << 31) - 1; // 2.15x10^ 9 constexpr ll INFLL = 1LL << 60; // 1.15x10^18 constexpr ll INFLL_LIM = (1LL << 62) - 1 + (1LL << 62); // 9.22x10^18 constexpr double EPS = 1e-9; constexpr int MOD = 1000000007; constexpr double PI = 3.141592653589793238462643383279; int dp[200005][2][2]; // dp[i][iから右に降りれるか][iが最後か] = min signed main() { INIT; VAR(int, n, p); VEC(int, h, n); REP(i, 200005) REP(j, 2) REP(k, 2) dp[i][j][k] = INFLL; dp[0][1][1] = 0; REP(i, n-1) { int toL = std::min(p, std::max(0LL, h[i] - h[i + 1])); int toR = std::min(p, std::max(0LL, h[i + 1] - h[i])); // 0 0 CHMIN(dp[i + 1][0][0], dp[i][0][0] + toL); CHMIN(dp[i + 1][1][0], dp[i][0][0] + std::min(toL + toR, p)); CHMIN(dp[i + 1][1][1], dp[i][0][0] + p); // 1 0 CHMIN(dp[i + 1][0][0], dp[i][1][0] + toR); CHMIN(dp[i + 1][1][0], dp[i][1][0] + toR); CHMIN(dp[i + 1][1][1], dp[i][1][0] + p); // 1 1 CHMIN(dp[i + 1][0][0], dp[i][1][1] + p); CHMIN(dp[i + 1][1][0], dp[i][1][1] + INFLL); CHMIN(dp[i + 1][1][1], dp[i][1][1] + toR); } int ans = INFLL; REP(j, 2) REP(k, 2) CHMIN(ans, dp[n-1][j][k]); OUT(ans)BR; return 0; }