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  1. #include <bits/stdc++.h>
  2.  
  3. using namespace std;
  4.  
  5. #define ll long long
  6. #define ull unsigned ll
  7. #define ld long double
  8. typedef vector<int> vi;
  9. typedef multiset<int> mi;
  10. typedef multiset<ll> mll;
  11. typedef vector<ll> vll;
  12. typedef vector<bool> vb;
  13. typedef vector<string> vs;
  14. typedef set<ll> sll;
  15. typedef vector<vector<int>> _2vi;
  16. typedef vector<vector<ll>> _2vll;
  17. #define all(v) ((v).begin()), ((v).end())
  18. #define sz(v) ((ll)((v).size()))
  19.  
  20. #define vinp(v, n) \
  21.   for (ull i = 0; i < (n); i++) \
  22.   cin >> (v)[i]
  23. #define printv(v) \
  24.   for (auto i : (v)) \
  25.   cout << i << " "
  26. #define fr0(i, n) for (ull(i) = 0; (i) < (n); (i)++)
  27. #define fr1(i, n) for (ull(i) = 1; (i) < (n); (i)++)
  28. #define fr(i, x, n) for (ull(i) = (x); (i) < (n); (i)++)
  29. #define _CRT_SECURE_NO_WARNING
  30. const ll MOD = 1000000007;
  31.  
  32. void Bustany() {
  33. ios_base::sync_with_stdio(false);
  34. cin.tie(NULL);
  35. cout.tie(NULL);
  36. #ifndef ONLINE_JUDGE
  37. freopen("./in.txt", "r", stdin), freopen("./out.txt", "w", stdout);
  38. #endif
  39. }
  40.  
  41. const ll N = 1e5 + 5;
  42. vector<sll> adj(N);
  43. //_2vll adj(N,vll(N));
  44. vb vis;
  45. ll n, m;
  46. vll v;
  47.  
  48. bool can(ll time) {
  49. vll x = v;
  50. ll last = n - 1;
  51. fr0(i, m) {
  52. ll t = time;
  53. while (last >= 0 && x[last] == 0) {
  54. last--;
  55. }
  56. t -= last + 1;
  57. if(t<=0){
  58. break;
  59. }
  60. while(last>=0 && x[last]<=t){
  61. t-=x[last];
  62. last--;
  63. }
  64. if(last>=0){
  65. x[last]-=t;
  66. }
  67. }
  68. return last==-1;
  69. }
  70.  
  71.  
  72. void solve() {
  73. cin >> n >> m;
  74. v.assign(n, {});
  75. vinp(v, n);
  76. ll l = 1, r = 1e5 + 1e14, ans, mid;
  77. while (l <= r) {
  78. mid = (l + r) / 2;
  79. if (can(mid)) {
  80. r = mid - 1;
  81. ans = mid;
  82. } else {
  83. l = mid + 1;
  84. }
  85. }
  86. cout << ans;
  87. }
  88.  
  89. int main() {
  90. Bustany();
  91. ll t = 1;
  92. // cin >> t;
  93. while (t--) {
  94. solve();
  95. }
  96. }
Success #stdin #stdout 0.01s 7740KB
stdin
Standard input is empty
stdout
1