Why does this program print 25 instead of 27 if I input 5? [duplicate]

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• Why are these constructs (using ++) undefined behavior? 8 answers

int main(void)
{

  int i; 
  scanf( "%d", &i );   
  i = i++ * i++ ;
  printf( "%d", i );
  getchar();
  getchar();
  return 0; 

}

Why does this program print 25 instead of 27 if I input 5 ?