public static void main(String[] args) {
double PI = 0.0, z = 4.0, i = 1.0;
int n = 1;
while(true) {
PI += -Math.pow(-1, n) * z / i;
n++;
i+=2;
if(PI > 3.1415 && PI < 3.1416) {
break;
}
}
System.out.println(PI);
}