Thanks for answers.
I write the code below:
#include <FreqCounter.h>
double frequency;
void setup() {
 pinMode(5,OUTPUT);
 pinMode(11,OUTPUT);
 pinMode(12,OUTPUT);
 pinMode(15,OUTPUT);
 pinMode(16,OUTPUT);
 pinMode(17,OUTPUT);
}
void loop() {
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long getFrequency(A0); {
#define SAMPLES 4096
long freq = 0;
for(unsigned int j=0; j<SAMPLES; j++) freq+= 500000/pulseIn(A0, HIGH, 250000);
frequency = freq/SAMPLES;
if (frequency <1) { digitalWrite(5, HIGH);
         digitalWrite(11,HIGH);}
if (frequency >=1) { digitalWrite(12, HIGH);
         digitalWrite(15,HIGH);}
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}
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}
No errors, but circuit doesen't work. I have mistakes in the code?