#include<math.h>
 
struct Coordinate{
    double x;
    double y;
    double z;
};
 
int main(void)
{
    struct Coordinate a = { 1, 5, 2 };
    struct Coordinate b = { 5, 3, 1 };
    struct Coordinate c = { 2, 8, 4 };
 
    double length_ab;
    double length_co;
 
    length_ab = sqrt( (b.x - a.x)*(b.x - a.x) + (b.y - a.y)*(b.y - a.y) + (b.z - a.z)*(b.z - a.z) );
    length_co = sqrt( c.x*c.x + c.y*c.y + c.z*c.z );
 
    if(length_ab > length_co){
        printf("length ab : %lf\n", length_ab );
    }
    else{
        printf("length co : %lf\n", length_co );
    }
 
    return 0;
}

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