public class sum {
/**
* @param args
*/
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
int n = Integer.parseInt(scanner.nextLine());
int x = -1;
float sum = 0;
for(int i=1;i<=n;i++){
x = x*(-1);
float fac = 1;
for(int j=1;j<=i;j++){
fac = fac*j;
}
float k = 1/fac;
sum = sum+x*k;
}
System.out.println("sum="+sum);
}
}
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