#include<stdio.h>
#include<math.h>
int isSqrNum(int n){	//kiem tra so chinh phuong 
	int iN;
	float fN;
	fN = sqrt(n);
	iN = fN;	
	if(iN==fN) return 1;
	return 0;	
}

int isPrime(int n){		//kiem tra so nguyen to
	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){		//tra ve so nguyen to thu n-th
	int i = 1, count = 0;
	while(1){
		i++;
		if(isPrime(i)) count++;
		if(count == n) return i;
	}
}

int main(){
	printf("Workshop2\n---------------------\n");
	int choice, n, i;
	printf("Homework1[1]\nHomework2[2]\nHomework3[3].\n---------------------\nwhat is your choice?>");
	scanf("%d", &choice);
	switch (choice){
		case 1:{	//homework1
			printf("enter your number which you wanna check>");
			scanf("%d", &n);
			if(isSqrNum(n)) printf("\nSquare number!");
			else printf("\nNot a square number!");
			break;
		}
		case 2:{	//homework2
			printf("enter your n-th of prime number output>");
			scanf("%d", &n);
			printf("prime number %d is %d", n, myPrime(n));
			break;
		}
		case 3:{	//homework3
			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);
			break;
		}
	}
	return 0;
}