function main(input) {
    var x = input[0]-0;
    var y = Math.floor(x/11);
    if(x-y*11>6) console.log(y*2+2);
    else if(x-y*11>0) console.log(y*2+1);
    else console.log(y*2);
}
main(require('fs').readFileSync('/dev/stdin', 'utf8').trim().split("\n"))
