foo.cpp: In function 'int main()':
foo.cpp:10:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(i=0;i<strlen(a);i++) x[i]=a[strlen(a)-i-1]-'0';
              ^
foo.cpp:11:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(j=0;j<strlen(b);j++) y[j]=b[strlen(b)-j-1]-'0';
              ^
foo.cpp:12:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(i=0;i<strlen(a);i++)
              ^
foo.cpp:13:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for(j=0;j<strlen(b);j++)
                  ^
foo.cpp:15:14: error: incompatible types in assignment of 'int' to 'int [1000]'
             s+=x[i]*y[j];
              ^
foo.cpp:16:18: error: invalid operands of types 'int [1000]' and 'int' to binary 'operator/'
             s+=s/10;
                  ^
foo.cpp:17:14: error: invalid operands of types 'int [1000]' and 'int' to binary 'operator%'
             s%=10;
              ^
foo.cpp:17:14: error:   in evaluation of 'operator%=(int [1000], int)'
foo.cpp:23:4: error: incompatible types in assignment of 'int' to 'int [1000]'
   s+=s[i]/10;
    ^
foo.cpp:29:4: error: incompatible types in assignment of 'int' to 'int [1000]'
   s+=s[i]/10;
    ^