#include<bits/stdc++.h>
#define re register
using namespace std;
inline int read(){
	re int t=0;re char v=getchar();
	while(v<'0')v=getchar();
	while(v>='0')t=(t<<3)+(t<<1)+v-48,v=getchar();
	return t;
}
int n,m,ans;
int main(){
	n=read();m=read();
	if(m>=n)puts("unsafe");
	else puts("safe");
}