View Compilation Error

0_0_15254598_4412.cpp:16:32: error: two or more data types in declaration of 'substr'
 int substr(string &a, string &b){
                                ^
0_0_15254598_4412.cpp: In function 'int main()':
0_0_15254598_4412.cpp:29:56: error: 'substr' was not declared in this scope
             cout<<subseg(s[x], s[y])<<substr(s[x], s[y]);
                                                        ^