#include<stdio.h>
    int fun(int x, int y)
    {
        if (x != y)
            return ((x + y) / 2);
        else return (x);
    }
    main()
    {
        int a = 4, b = 5, c = 6;
        printf("%d\n", fun (2*a,fun(b,c)));
    }

我原来把循环条件看成不成立了，执行后面的else了，感谢大神指教……