divide 2

int div2(int a){
    if(a & 1) a += -1;
    if(a & 2) a += -2 + 1;
    if(a & 4) a += -4 + 2;
    if(a & 8) a += -8 + 4;
    if(a & 16) a += -16 + 8;
    if(a & 32) a += -32 + 16;
    if(a & 64) a += -64 + 32;
    if(a & 128) a += -128 + 64;
    if(a & 256) a += -256 + 128;
    if(a & 512) a += -512 + 256;
    if(a & 1024) a += -1024 + 512;
    if(a & 2048) a += -2048 + 1024;
    if(a & 4096) a += -4096 + 2048;
    if(a & 8192) a += -8192 + 4096;
    if(a & 16384) a += -16384 + 8192;
    if(a & 32768) a += -32768 + 16384;
    if(a & 65536) a += -65536 + 32768;
    if(a & 131072) a += -131072 + 65536;
    if(a & 262144) a += -262144 + 131072;
    if(a & 524288) a += -524288 + 262144;
    if(a & 1048576) a += -1048576 + 524288;
    if(a & 2097152) a += -2097152 + 1048576;
    if(a & 4194304) a += -4194304 + 2097152;
    if(a & 8388608) a += -8388608 + 4194304;
    if(a & 16777216) a += -16777216 + 8388608;
    if(a & 33554432) a += -33554432 + 16777216;
    if(a & 67108864) a += -67108864 + 33554432;
    if(a & 134217728) a += -134217728 + 67108864;
    if(a & 268435456) a += -268435456 + 134217728;
    if(a & 536870912) a += -536870912 + 268435456;
    if(a & 1073741824) a += -1073741824 + 536870912;
    if(a & 2147483648) a += -2147483648 + 1073741824;
    return a;
}