#include<stdio.h>
#include<math.h>

int isPrime(int n){		
	int i;
	if(n < 2) return 0;
	for(i = 2; i < n; i++)
		if(n % i == 0) return 0;
	return 1;
}

int myPrime(int n){		
	int i = 1, count = 0;
	while(1){
		i++;
		if(isPrime(i)) count++;
		if(count == n) return i;
	}
}
int main(){
	int i, n;
	float sum = 0;
	printf("enter your n-th to sum:");
	scanf("%d", &n);
	for(i = 1; i <= n; i++){
		sum += 1.0 / pow(myPrime(i), 2);
	}
	printf("\nP = %f", sum);
}