#includeint main(){ int n,i; int a = 1,b = 1,c = 1; float sum = 0.0; scanf("%d",&n); for(i = 0;i < n;i++) { sum += c*(float)(a)/b; b = a+b; a = b-a; c = -c; } printf("sum=%f\n",sum); return 0;}
