for i in $(seq 1 5); do time ./int_sort_20.o; done
       96.96 real        95.21 user         0.79 sys
       96.84 real        95.06 user         0.83 sys
       96.88 real        95.07 user         0.86 sys
       96.96 real        95.19 user         0.80 sys
       96.92 real        95.10 user         0.86 sys