foo.cpp: In function 'int cal()':
foo.cpp:8:17: warning: unused variable 't' [-Wunused-variable]
  int s = 0; int t = 0;
                 ^
foo.cpp:9:6: warning: unused variable 'needT1' [-Wunused-variable]
  int needT1;
      ^
foo.cpp:70:6: warning: unused variable 'maxT3' [-Wunused-variable]
  int maxT3, needT3, doT3;
      ^
foo.cpp:70:21: warning: unused variable 'doT3' [-Wunused-variable]
  int maxT3, needT3, doT3;
                     ^
foo.cpp: In function 'int main()':
foo.cpp:113:16: error: 'system' was not declared in this scope
  system("pause");
                ^