function bus(input){
    let startingPassengers=Number(input.shift());
    let stops=Number(input.shift());
    
 
    for (let i=1; i<=stops; i++){
        if (i%2!=0){
            startingPassengers+=2;
        } else {
            startingPassengers-=2;
        }
        let slizashti=Number(input.shift());
        startingPassengers-=slizashti;
        let kachvashtiSe=Number(input.shift());
        startingPassengers+=kachvashtiSe;
    }

    console.log(`The final number of passengers is : ${startingPassengers}`);

}