Function countBit

CPP/bitmasking/count_bits.cpp:8–16

#define mod 1000000007
#define endl '\n'
int countBit(int n){
int count=0;
    while(n>0){
        int last=(n&1);
        count+=last;
        n=n>>1;
    }
    return count;
}
int countBit_fast(int n){
    int ans=0;
    while(n>0){