#include <stdio.h>
//#include <math.h>
#define MIN(x,y) (((x) > (y)) ? (y) : (x))
#define ABS(x) ((x) >= 0 ? (x) : (-(x)))
int main() {
  int w, s;
  scanf("%d %d", &s, &w);
  printf("%s", w >= s ? "unsafe" : "safe");
  return 0;
}