Binary and 3

$2^k \equiv 1 \mod 3$ if $k \equiv 0 \mod 2$

$2^k \equiv 2 \mod 3$ if $k \equiv 1 \mod 2$

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#include <stdio.h>
int main()
{
    char c;
    int count = 0, sum = 0, bit;
    char rem_two = 0;
    scanf("%c", &c);
    while(c == '1' || c == '0'){
        bit = c - 48;
        sum += (rem_two ? 2 : 1) * bit;
        sum %= 3;
        if(sum == 0) count += 1;
        rem_two = ~rem_two;
        scanf("%c", &c);
    }
    printf("%d", count);
}