Each day do one impossible thing...
    Consider:
    void main() {
        int a;
        scanf("%d",&a);
        while (a< 5) { a = a *1; }
    }

    If a<5 then this loops forever (does not HALT)
    Probably meant plus instead of times (?)

    Would it not be nice if we had a procedure HALTS
    int  HALTS(program)
    which would return 0 if any input caused the program
    to loop forever?

    Or even if we had
    int HALTS(program,input)
    which would return 1 if  program is a valid program and
    eventually halts when given input.

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