#include<stdio.h>
#include<math.h>
int main()
{
double x,q,c;
while(1){
if(q==-1)break;
x=q/2;
while(fabs(x
*x
*x
-q
)>0.0000001*q
){ c=x-(x*x*x-q)/(3*x*x);
x=c;
}
}
return 0;
}
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