Alternate

#include<stdio.h>

int main()
{
    double l, t;
    int m;
    scanf("%lf%lf%d", &l,&t,&m);

    if(m==1) t-=10;
    else if(m==2) t-=20;
    else t-=30;

    l/=1000;
    t/=60;

    double s=l/t;
    s*=100;
    s=round(s);
    s/=100;

    printf("%.2lf\n", s);

    return 0;
}