- #include <iostream> 
- using namespace std; 
-   
- int main() { 
-     long long s,sum=1,p=1,n=1; 
-     cin >> s; 
-     while (sum<s){  
- 		n++; 
-         p=p*2+n; 
-         sum += p; 
-     } 
-     cout << n; 
-     return 0; 
- } 
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