1/S=1/51+1/52.+1/60
1/S＜1/51+1/51.+1/51
＜10/51
S＞51/10=5.1
1/S＞1/60+.1/60
＞10/60
＞1/6
S＜6
综上5.1＜S＜6
∴S的整数部分是5