编辑代码

#include <stdio.h>
float fee (float D){
    float M = 0;
    if(D <= 3) {
            M = 12;
    }else{
            M = 12 + (2.5 * (D - 3));
    }
    return M;
}
int main () {
    float D = 0;
    float M = 0;
    while(D >= 0) {
        scanf("%f",&D);
        M = fee(D);
        printf("%f\n",M);
    }
	return 0;
}