CodeForces Round #280 (Div.2)

#include<stdio.h>
int main()
{
    int i,n;
    int s1,s2;
    while(scanf("%d",&n)!=EOF)
    {
        for(i=1;i<=100;i++)
        {
            s1=i*(i+1)*(i+2)/6;
            s2=(i+1)*(i+2)*(i+3)/6;
            if(n>=s1&&n<s2)
            {
                printf("%d\n",i);
                break;
            }
            
        }
    }
}