#include <stdio.h> #include <math.h> #include <vector> using namespace std; int main() { long long n; while (scanf("%lld",&n) != EOF) { vector<long long> nums; nums.push_back((long long)sqrt(2*n)-1); nums.push_back((long long)sqrt(2*n)); nums.push_back((long long)sqrt(2*n)+1); int tmp=0; for (int i=0;i<nums.size();i++) { if (nums[i]*nums[i]-nums[i]+2<=2*n && 2*n<=nums[i]*nums[i]+nums[i]) { tmp = nums[i]; break; } } printf("%d\n",tmp); } }