foo.cpp: In function 'int main()':
foo.cpp:10:11: error: 'strlen' was not declared in this scope
 l=strlen(s);
           ^
foo.cpp:7:9: warning: unused variable 'n' [-Wunused-variable]
 int t,m,n,i,j,k,l,o;
         ^
foo.cpp:7:15: warning: unused variable 'k' [-Wunused-variable]
 int t,m,n,i,j,k,l,o;
               ^