const main = (input) => {
    input = input.split(' ');
    const S = parseInt(input[0]);
    const W = parseInt(input[1]);

    if (S <= W) {
        console.log('unsafe');
    } else {
        console.log('safe');
    }
};

// 標準入力
main(require('fs').readFileSync('/dev/stdin', 'utf8'));