#include <stdio.h>

// 00000000 00000000 00000001 00000001 00000000 00000000

void encode (char a[], int length, char b[])
{
    int k=0;

    if(length%3 !=0)
            length = length + ( 3 - (length - (length/3*3)));
    int padding = 3 - (length-(length/3*3)) -1;

    for(int i=0;i<length/3;i++)
    {
        int val=0;
        val=val+(a[i*3]<<16);
        val=val+(a[i*3+1]<<8);
        val=val+a[i*3+2];
        b[k++]=(val&((~(~0<<6))<<18))>>18;
        b[k++]=(val&((~(~0<<6))<<12))>>12;
        b[k++]=(val&((~(~0<<6))<<6))>>6;
        b[k++]=val&(~(~0<<6));
    }

    for(int i=0; i<k-padding; ++i)
    {
        if(b[i]<('Z'-'A'))
            printf("%c", b[i]+'A');
        else if(b[i]<('Z'-'A')+('z'-'a'))
            printf("%c", b[i]-('Z'-'A')+'a');
        else if(b[i]<('Z'-'A')+('z'-'a')+('9'-'0'))
            printf("%c", b[i]-('Z'-'A')-('z'-'a')+'0');
        else if(b[i]==62)
            printf("+");
        else printf("/");
    }

    for(int i=0;i<padding;i++)
        printf("=");
    printf("\n");
}

int main()
{
  char a[20]={0, 0, 1, 1};

  char b[20]={0};

  encode(a,4,b);

  return 0;

}