C :

#include<stdio.h>
#include<math.h>
int main()
{int s=0,n=0;
while(s<=1000)
{n++;s=s+n;}


printf("%d",n);
	return 0;
}

C++ :

#include<iostream>
using namespace std;
int main()
{
  int n=0,s=0;
  while(s<=1000)
  {
    ++n;
    s+=n;
  }
  cout<<n;
  return 0;
}