#include <stdio.h>
int main()
{
int I= 5;
int J= 4;
int K= 4;
for (int i=1; i<=I; i++) {
for (int j=1; j<=J; j++) {
for (int k=1; k<=K; k++) {
fprintf(stderr,"y%d_%d_%d", i, j, k);
if (k < K || j < J)
fprintf(stderr," + ");
}
}
fprintf(stderr," <= %d\n", i);
}
}