include<stdio.h>

include<math.h>

int main()
{
long h;
while(scanf("%ld",&h)!=EOF)
{

    for(long i=sqrt(h);i>0;i--)
    {
        if(h==1)
        {
            printf("0\n");
        }
        if((i*i+i)<=h)
        {
            printf("%ld\n",i);
            break;
        }

    }
}
return 0;

}