Lets say you have take an input of 10^5 numbers, there are many methods

1. std::cin>>x

you can use std::cin which is a standard method to obtain input from STDIN how ever there are better methods

2. scanf("%d",&x);

scanf / printf are roughly thrice as fast as the cin/cout

3. FAST IO
    void fastscan(int &x)
    {
        bool neg=false;
        register int c;
        x =0;
        c=getchar();
        if(c=='-')
        {
            neg = true;
            c=getchar();
        }
        for(;(c>47 && c<58);c=getchar())
            x = (x<<1) + (x<<3) +c -48;
        if(neg)
            x *=-1;
    }

fastscan(x);

this is one of the fastest way to take an integer input from STDIN this is around 10 times faster than scanf() This is very useful in competetive programming

NOTE : You can add ios_base::sync_with_stdio(false); in main() function to make your cin adn cout faster