Why doesn't variable change values? C

Hi guys, I'm creating a small little program. I was wondering why my variables are staying at their initialized values instead of what the input is supposed to change it to. Originally I was scanning in the double wrong, but I"m pretty sure I'm doing it correctly, correct?

#include <stdio.h>

int main(){

double length = 0.0;

printf("Enter number: ");

scanf("%1f", &length);
printf("%f", length);

return 0;

Any help please?