View Compilation Error

0_0_19539156_20014.cpp: In function 'int main()':
0_0_19539156_20014.cpp:10:3: error: 'sum' was not declared in this scope
   sum=n*n;
   ^
0_0_19539156_20014.cpp:14:11: error: 's2' was not declared in this scope
   else if(s2==0)
           ^
0_0_19539156_20014.cpp:17:27: error: 's1' was not declared in this scope
             printf("%d\n",s1-(k-mod)*(k-mod));
                           ^
0_0_19539156_20014.cpp:19:27: error: 's1' was not declared in this scope
             printf("%d\n",s1-mod*mod);
                           ^