#includeint main() { int i,n,sum=0,a=0,b=1,c; scanf("%d",&n); for(i=1;i<=n;i++) { c=a; a=b; b=a+c; sum+=a; } printf("%d",sum); return 0; }

#includeint main() { int i,n,sum=0,a=0,b=1,c; scanf("%d",&n); for(i=1;i<=n;i++) { c=a; a=b; b=a+c; sum+=a; } printf("%d",sum); return 0; }