#include "stdio.h"
 #include "math.h"
double pin (float x, int N)
{   double y;
    if(N==0) return 0;
    else y=sqrt(x+pin(x,N-1));
    return y;
 }
main()
{   float x,y;
    int N;
    printf("please input x and N:");
    scanf("%f%d",&x,&N);
    y=pin(x,N);
    printf("y=%f\n",y);
 }