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  1. #include<stdio.h>
  2. typedef long long lld;
  3.  
  4. inline int g(int x) {
  5.     int le = 1, ri = x, ans = ri;
  6.     x += x;
  7.     while (le <= ri) {
  8.         lld mid = (le + ri) >> 1;
  9.         if (mid * (mid + 1) >= x) ans = mid, ri = mid - 1;
  10.         else le = mid + 1;
  11.     }
  12.     if (x == (lld)(ans)*(ans+1)) return ans;
  13.     else --ans;
  14.     x /= 2;
  15.     int sum = ((lld)(ans))*(ans+1)/2;
  16.     return ans%2 ? (x-sum)%2+ans+1 : -2*((x-sum)%2)+ans+3;
  17. }
  18.  
  19. int main()
  20. {
  21.     int n;
  22.     scanf("%d", &n);
  23.     printf("%d\n", g(n<0?-n:n));
  24.     return 0;
  25. }
  26.  
Success #stdin #stdout 0s 2172KB
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https://ideone.com/SNwFCK
language:
C (gcc 8.3)
created:
9 years ago
visibility:
public

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