#include <stdio.h>
int main() {
    int a, b;
    float hour, min, tangle;
    scanf_s("%d:%d", &a, &b);
    if (a >= 12)
        a -= 12;
    hour = a * 30 + b * 0.5;
    min = b * 6;
    if (min > hour)
        tangle = min - hour;
    else
        tangle = hour - min;
    if (tangle > 180)
        tangle = 360 - tangle;  //易错
    printf("%.1f", tangle);
    return 0;
}

/sandbox/1/a.c:6:2: warning: implicit declaration of function 'scanf_s' is invalid in C99 [-Wimplicit-function-declaration]
        scanf_s("%d:%d", &a, &b);
        ^
1 warning generated.
/tmp/a-b069bc.o: In function `main':
a.c:(.text+0xf): undefined reference to `scanf_s'
clang: error: linker command failed with exit code 1 (use -v to see invocation)