#include <math.h>
#include <stdio.h>
typedef double r;
#define M 3
r n[M] = {3, 4, 2.3};
int main(){int j=M; r s=0; while(j--) s += n[j]*n[j];
if(0) {int j = M; r a = 1/sqrt(s); while(j--) n[j] *= a; s=1;}
{r m[M][M]; {int j=M; while(j--){int k=M; while(k--) m[j][k] = j==k?s:0;}}
 void pm(char * s){int j, k; for(j=0; j<M; ++j)
   {for(k=0; k<M; ++k) printf("%9.6f ", m[j][k]); printf(" %s\n", s);}}
pm("before");
{int j=M; while(j--){int k=M; while(k--) m[j][k] -= 2*n[k]*n[j];}}
pm("after");}
return 0;}