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

int main(){
int n,i,j;
double suma=0;
double gornji,clan;
double donji=0;

do{
    printf("\n\tMolimo unesite vrednost za N-> ");
    scanf("%d",&n);
} while(n<=0);

for(i=1;i<n;i++){

    gornji=pow(-2,i);
    donji+=i;
    clan=gornji/donji;

    printf("\n\tclan[i=%d]= %lf",i,clan);
    suma+=clan;

}
    printf("\n\tsuma= %lf\t",suma);







return 0;
}