fork 함수 반복할 때 exit

#include <stdio.h>
#include <stdlib.h>
void main(){
   int x, i;
   for(i=0;i<5;i++){
      x=fork();
      if (x==0){ // child
         int k;
         for(k=0;k<10;k++){
            printf("%d-th child running %d-th iteration “, i, k);   
            fflush(stdout);         // to make printf work immediately
            sleep(1);              // sleep 1 second
        }
        exit(0);   // child exits after 10 iterations
      }
}
   // now parent
   printf(“parent exits\n”);
}
 
printf에서 i와 k 값을 출력할 때 왜 i 값이 일정하지 않게 나오나요??