Keliling lingkaran (C)

#include 
#include 


float keliling(float jari);
int main(){
    float kel, r;
    
    printf("Masukkan jari-jari : ");
    scanf("%f",&r);
    
    kel=keliling(r);
    
    printf("Keliling lingkaran : %f",kel);
    
    getche();
    return 0;
}

float keliling(float jari){
     float hasil;
     hasil=2*jari*22/7;
     return hasil;      
      
}