foo.cc:3:1: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
    3 | main()
      | ^~~~
foo.cc: In function 'int main()':
foo.cc:6:13: warning: unused variable 'i' [-Wunused-variable]
    6 |     int n,m,i,f=0,t=0,s=0;
      |             ^

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