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http://acm.zju.edu.cn/onlinejudge/showProblem.do?problemCode=2855

#include<stdio.h>
#include<string.h>
#include<math.h>
double PI = acos(-1) ;
double N = log(tan(PI/4 + (85*PI/180)/2)) ;
double S = log(tan(PI/4 + (-85*PI/180)/2)) ;
double W = -PI ;
double E = PI ;
double n, s, w, e ;
double longitude, latitude ;
int t ;
void judge(double p, double q)
{
    if(p>(w+e)/2)
    {
        w = (w+e)/2 ;
        if(q>(n+s)/2)
        {
            s = (s+n)/2 ;
            printf("r") ;
        }
        else
        {
            n = (n+s)/2 ;
            printf("s") ;
        }
    }
    else
    {
        e = (w+e)/2 ;
        if(q>(n+s)/2)
        {
            s = (s+n)/2 ;
            printf("q") ;
        }
        else
        {
            n = (n+s)/2 ;
            printf("t") ;
        }
    }
}
int main()
{
    int i ;
    //freopen("a.txt","r",stdin) ;
    //freopen("b.txt","w",stdout) ;
    while(scanf("%lf%lf%d",&longitude,&latitude,&t)!=EOF)
    {
        n = N ; s = S; w = W; e = E ;
        double p = (longitude*PI)/180 ;
        double q = log(tan(PI/4 + (latitude*PI/180)/2)) ;
        printf("t") ;
        for(i=0; i<t; i++)
        {
            judge(p, q) ;
        }
        printf("\n") ;
    }
    return 0 ;
}