45: Gold

45: Gold

#include <stdio.h>
int main()
{
	int n,sum=0,k=1;
	scanf("%d",&n);
	while(k<=n)n-=k,sum+=k*k,k++;
	printf("%d\n",sum+=n*k);
	return 0;	
}

#include <stdio.h>
int main()
{
	int i,j,n,sum=0,k=1;
	scanf("%d",&n);		
	for(i=1;i<=141;++i)
	    for(j=1;j<=i;++k,++j)
	    {
	        if(k!=n)sum+=i;
	        else{printf("%d\n",sum+i);return 0;}
	    }
}