def interpret(code):
    memory = [0]*1000
    loopstack = []
    mpointer, cpointer = 0,0
    while cpointer < len(code):
        char = code[cpointer]
        if char == '+':
            memory[mpointer]+=1
            if memory[mpointer] == 256:
                memory[mpointer] = 0
        elif char == '-':
            memory[mpointer]-=1
            if memory[mpointer] == -1:
                memory[mpointer] = 255
        elif char == '<':
            mpointer-=1
        elif char == '>':
            mpointer+=1
        elif char == '.':
            sys.stdout.write(chr(memory[mpointer]))
        elif char == '[':
            startpos = cpointer + 1
            try:
                if memory[mpointer] != 0:
                    loopstack.append(cpointer)
                else: # skip loop
                    counter = 1
                    while counter > 0:
                        cpointer+=1
                        char = code[cpointer]
                        if char == '[':
                            counter+=1
                        elif char == ']':
                            counter-=1
            except IndexError:
                print("Unmatched [ at pos " + str(startpos))
                return
        elif char == ']':
            try:
                if memory[mpointer] != 0:
                    cpointer = loopstack[-1]
                else:
                    loopstack.pop()
            except IndexError:
                print("Unmatched ] at pos " + str(cpointer + 1))
                return
        cpointer+=1