#include <iostream>
#include <vector>
#include <queue>
#include <algorithm>
using namespace std; 
#define pb push_back 
#define rep(i,a,b) for(int i=a;i<=b;i++)
#define ll long long
#define sc(x) scanf("%d",&x)
#define sl(x) scanf("%lld",&x)
/* run this program using the console pauser or add your own getch, system("pause") or input loop */

int main(int argc, char** argv) {
	int s,f;
	cin>>s>>f;
	if(f>=s)
	{
		printf("unsafe")
;	}
else puts("safe");
	return 0;
}