int from64_to10(char num[]){
   int to =62;
   char dict[62] = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
   char ret[]  = "";
   int len = strlen(num);
   int dec =0;
   int i,j;
   for(i=0;i<len;i++){
     for(j=0;j<62;j++){
       if(dict[j] == num[i]){
           dec += j*pow(62,len-i-1);

       }
     }
   }
   return dec;

}

void from10_to62(int num, char ret[1024]){
   int to =62;
   char dict[62] = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";

   char val;
   int len;
   while(num > 0){
     val = dict[num%to];
     len = strlen(ret);
     ret[strlen(ret)] = val;
     num = num/to;
  }
}